diff --git a/backend/src/group/dependencies.py b/backend/src/group/dependencies.py
index 4d916835..cbf07a9f 100644
--- a/backend/src/group/dependencies.py
+++ b/backend/src/group/dependencies.py
@@ -11,7 +11,7 @@
 from src.subject.utils import has_subject_privileges
 
 from . import service
-from .exceptions import AlreadyInGroup, GroupNotFound, MaxCapacity
+from .exceptions import AlreadyInGroup, AlreadyInGroupOfProject, GroupNotFound, MaxCapacity
 
 
 async def retrieve_group(
@@ -79,5 +79,9 @@ async def join_group(
     if len(group.members) >= project.capacity:
         raise MaxCapacity()
 
+    groups = await retrieve_groups_by_user(user, db)
+    if any([group.project_id == g.project_id for g in groups]):
+        raise AlreadyInGroupOfProject()
+
     await service.join_group(db, group_id, uid)
     return await service.get_group_by_id(db, group_id)
diff --git a/backend/src/group/exceptions.py b/backend/src/group/exceptions.py
index 9fda0c9e..c55c03af 100644
--- a/backend/src/group/exceptions.py
+++ b/backend/src/group/exceptions.py
@@ -17,3 +17,9 @@ class MaxCapacity(HTTPException):
     def __init__(self):
         """Raised when user wants to join group at max capacity"""
         super().__init__(status_code=403, detail="Group at max capacity")
+
+
+class AlreadyInGroupOfProject(HTTPException):
+    def __init__(self):
+        """Raised when person is already in another group of the project"""
+        super().__init__(status_code=403, detail="Already in a Group for this project")
diff --git a/backend/src/subject/router.py b/backend/src/subject/router.py
index ca0b9eef..f5edb649 100644
--- a/backend/src/subject/router.py
+++ b/backend/src/subject/router.py
@@ -97,6 +97,8 @@ async def create_subject_instructor(
 ):
     if await service.is_instructor(db, subject_id, user.uid):
         raise AlreadyInstructor()
+    if await service.is_student(db, subject_id, user.uid):
+        raise AlreadyRegistered()
     await service.add_instructor_to_subject(db, subject_id, user.uid)
 
 
@@ -129,6 +131,8 @@ async def add_student_to_subject(
     user: User = Depends(retrieve_user),
     db: AsyncSession = Depends(get_async_db)
 ) -> Subject:
+    if await service.is_instructor(db, subject.id, user.uid):
+        raise AlreadyInstructor()
     if await service.is_student(db, subject.id, user.uid):
         raise AlreadyRegistered()
     await service.create_subject_student(db, subject.id, user.uid)
diff --git a/backend/src/subject/service.py b/backend/src/subject/service.py
index 5f5e517b..5ee276f2 100644
--- a/backend/src/subject/service.py
+++ b/backend/src/subject/service.py
@@ -63,7 +63,7 @@ async def is_instructor(db: AsyncSession, subject_id: int, uid: str) -> bool:
 
 async def create_subject(db: AsyncSession, subject: SubjectCreate) -> Subject:
     db_subject = Subject(
-        name=subject.name, academic_year=subject.academic_year)
+        name=subject.name, academic_year=subject.academic_year, email=subject.email)
     db.add(db_subject)
     await db.commit()
     await db.refresh(db_subject)
diff --git a/frontend/src/components/form_elements/FilesInput.vue b/frontend/src/components/form_elements/FilesInput.vue
index a44d8405..005a7cef 100644
--- a/frontend/src/components/form_elements/FilesInput.vue
+++ b/frontend/src/components/form_elements/FilesInput.vue
@@ -45,9 +45,11 @@ function onAddFilesClick() {
 }
 
 function updateFiles(event: Event) {
-    // todo: check of meerdere identieke filenames aanwezig zijn
     const files = (event.target as HTMLInputElement).files!;
-    inputFiles.value.push(...files);
+    const unique_files = Array.from(files).filter(
+        (file) => !inputFiles.value.map((file) => file.name).includes(file.name)
+    );
+    inputFiles.value.push(...unique_files);
 }
 
 function onDeleteClick(index: number) {
diff --git a/frontend/src/components/groups/GroupCard.vue b/frontend/src/components/groups/GroupCard.vue
index 46963879..7e8c9946 100644
--- a/frontend/src/components/groups/GroupCard.vue
+++ b/frontend/src/components/groups/GroupCard.vue
@@ -1,28 +1,30 @@
 <template>
     <v-card class="groupcard" variant="flat">
-        <v-row>
-            <v-col cols="7">
-                <StudentsDialog
-                    :students="group.members"
-                    :title="$t('project.group', { number: group.num })"
-                />
-                <v-btn v-if="isTeacher" variant="flat" @click="toGroupPage">
-                    {{ $t("group.to_grouppage") }}
-                </v-btn>
-            </v-col>
-            <v-col cols="2">
-                {{ amountOfMembers + "/" + project.capacity }}
-            </v-col>
-            <v-col cols="3">
-                <GroupButtons
-                    :amountOfMembers="amountOfMembers"
-                    :group="group"
-                    :project="project"
-                    :user="user"
-                    :isTeacher="isTeacher"
-                />
-            </v-col>
-        </v-row>
+        <v-container>
+            <v-row>
+                <v-col cols="7">
+                    <StudentsDialog
+                        :students="group.members"
+                        :title="$t('project.group', { number: group.num })"
+                    />
+                    <v-btn v-if="isTeacher" variant="flat" @click="toGroupPage">
+                        {{ $t("group.to_grouppage") }}
+                    </v-btn>
+                </v-col>
+                <v-col cols="2">
+                    {{ amountOfMembers + "/" + project.capacity }}
+                </v-col>
+                <v-col cols="3">
+                    <GroupButtons
+                        :amountOfMembers="amountOfMembers"
+                        :group="group"
+                        :project="project"
+                        :user="user"
+                        :isTeacher="isTeacher"
+                    />
+                </v-col>
+            </v-row>
+        </v-container>
     </v-card>
 </template>
 
diff --git a/frontend/src/components/home/listcontent/DeadlineItem.vue b/frontend/src/components/home/listcontent/DeadlineItem.vue
index e593015f..5690f59d 100644
--- a/frontend/src/components/home/listcontent/DeadlineItem.vue
+++ b/frontend/src/components/home/listcontent/DeadlineItem.vue
@@ -1,5 +1,5 @@
 <template>
-    <div class="projectbtn" @click="navigateToProject">
+    <router-link class="projectbtn" :to="`/project/${project.id}`">
         <div :class="submissionToClass(latestSubmissionStatus)"></div>
         <div class="leftcontent">
             <h3>{{ project.name }}</h3>
@@ -8,12 +8,11 @@
         <div class="rightcontent">
             {{ $d(project.deadline, "short") }}
         </div>
-    </div>
+    </router-link>
 </template>
 
 <script setup lang="ts">
 import { computed, toRefs } from "vue";
-import router from "@/router";
 import type Project from "@/models/Project";
 import type Submission from "@/models/Submission";
 import { Status } from "@/models/Submission";
@@ -44,10 +43,6 @@ function submissionToClass(submission: Submission | null) {
         none: !submission,
     };
 }
-
-const navigateToProject = () => {
-    router.push(`/project/${project.value.id}`);
-};
 </script>
 
 <style scoped>
@@ -60,6 +55,8 @@ const navigateToProject = () => {
     cursor: pointer;
     height: 65px;
     border-radius: 2px;
+    text-decoration: none;
+    color: inherit;
 }
 
 .projectbtn:hover {
diff --git a/frontend/src/components/home/listcontent/SubjectItem.vue b/frontend/src/components/home/listcontent/SubjectItem.vue
index d5182f36..a0b9d4cc 100644
--- a/frontend/src/components/home/listcontent/SubjectItem.vue
+++ b/frontend/src/components/home/listcontent/SubjectItem.vue
@@ -1,5 +1,5 @@
 <template>
-    <div class="coursebtn" @click="navigateToCourse">
+    <router-link class="coursebtn" :to="`/subjects/${subject.id}`">
         <div>
             <h3>{{ subject.name }}</h3>
             <v-skeleton-loader v-if="isInstructorsLoading" type="text" />
@@ -8,12 +8,11 @@
             </p>
         </div>
         <v-icon class="chevron" icon="mdi-chevron-right" />
-    </div>
+    </router-link>
 </template>
 
 <script setup lang="ts">
 import type Subject from "@/models/Subject";
-import router from "@/router";
 import { toRefs, computed } from "vue";
 import { useSubjectInstructorsQuery } from "@/queries/Subject";
 
@@ -34,10 +33,6 @@ const sortedInstructors = computed(() => {
         return b.is_teacher - a.is_teacher;
     });
 });
-
-const navigateToCourse = () => {
-    router.push(`/subjects/${subject.value.id}`);
-};
 </script>
 
 <style scoped>
@@ -51,6 +46,8 @@ const navigateToCourse = () => {
     cursor: pointer;
     background-color: rgb(var(--v-theme-background));
     border-radius: 2px;
+    text-decoration: none;
+    color: inherit;
 }
 
 .coursebtn:hover {
diff --git a/frontend/src/components/subject/createSubjectView/header/CreateSubjectHeaderCard.vue b/frontend/src/components/subject/createSubjectView/header/CreateSubjectHeaderCard.vue
index d522a9ad..fae6ed97 100644
--- a/frontend/src/components/subject/createSubjectView/header/CreateSubjectHeaderCard.vue
+++ b/frontend/src/components/subject/createSubjectView/header/CreateSubjectHeaderCard.vue
@@ -24,7 +24,7 @@
                         v-model="activeAcademicYear"
                         variant="outlined"
                         :items="academicYearItems"
-                        :item-title="(item) => `20${item}-20${item + 1}`"
+                        :item-title="(item) => `${item}-${item + 1}`"
                         :item-value="(item) => item"
                         :label="$t('subject.academy_year')"
                         required
diff --git a/frontend/src/components/subject/subjectview/header/SubjectHeaderCard.vue b/frontend/src/components/subject/subjectview/header/SubjectHeaderCard.vue
index 01078d80..5d397b66 100644
--- a/frontend/src/components/subject/subjectview/header/SubjectHeaderCard.vue
+++ b/frontend/src/components/subject/subjectview/header/SubjectHeaderCard.vue
@@ -12,9 +12,7 @@
                 </div>
                 <v-card-text>
                     <v-chip color="secondary" variant="flat" label class="academyyear">
-                        {{
-                            `${$t("subject.academy_year")} 20${academicYear}-20${academicYear + 1}`
-                        }}
+                        {{ `${$t("subject.academy_year")} ${academicYear}-${academicYear + 1}` }}
                     </v-chip>
                     <v-row class="instr-container">
                         <v-chip
diff --git a/frontend/src/components/submission/SubmissionCard.vue b/frontend/src/components/submission/SubmissionCard.vue
index 3d842221..3260c132 100644
--- a/frontend/src/components/submission/SubmissionCard.vue
+++ b/frontend/src/components/submission/SubmissionCard.vue
@@ -1,76 +1,80 @@
 <template>
-    <v-divider />
-    <v-card variant="flat">
-        <v-card-title>
-            {{ $t("submission.status") }}
-            <p v-if="new Date(submission.date) <= deadline" :class="Status[submission.status]">
-                {{ Status[submission.status] }}
-            </p>
-            <p v-else class="Deadline">{{ $t("submission.after_deadline") }}</p>
-        </v-card-title>
-        <v-card-subtitle>
-            {{ $t("submission.datetime") }} {{ $d(submission.date, "long") }}
-        </v-card-subtitle>
-        <v-card-item>
+    <div>
+        <v-divider />
+        <v-card variant="flat">
             <v-card-title>
-                {{ $t("submission.remarks") }}
-            </v-card-title>
-            <v-card-text v-if="submission.remarks">
-                {{ submission.remarks }}
-            </v-card-text>
-            <v-card-subtitle v-else>
-                {{ $t("submission.remarks_empty") }}
-            </v-card-subtitle>
-        </v-card-item>
-        <v-card-item v-if="submission.stderr || submission.stdout || submission.testresults.length">
-            <v-card-title>{{ $t("submission.docker_test") }}</v-card-title>
-            <v-card-text>
-                <p v-if="submission.stdout">Stdout: {{ submission.stdout }}</p>
-                <p v-if="submission.stderr">Sterr: {{ submission.stderr }}</p>
-                <ul>
-                    <li v-for="result in submission.testresults" :key="result">
-                        <p v-if="result.succeeded" class="text-green">{{ result.value }}</p>
-                        <p v-else class="text-red">{{ result.value }}</p>
-                    </li>
-                </ul>
-            </v-card-text>
-        </v-card-item>
-        <v-card-item>
-            <v-card-title>
-                {{ $t("submission.files") }}
+                {{ $t("submission.status") }}
+                <p v-if="new Date(submission.date) <= deadline" :class="Status[submission.status]">
+                    {{ Status[submission.status] }}
+                </p>
+                <p v-else class="Deadline">{{ $t("submission.after_deadline") }}</p>
             </v-card-title>
             <v-card-subtitle>
-                {{ $t("submission.download_info") }}
+                {{ $t("submission.datetime") }} {{ $d(submission.date, "long") }}
             </v-card-subtitle>
-            <v-container>
-                <v-alert
-                    v-if="isError"
-                    title="Error"
-                    color="error"
-                    :text="error!.message"
-                ></v-alert>
-                <v-skeleton-loader v-else :loading="isLoading" type="card">
-                    <v-col>
-                        <v-chip
-                            class="ma-2"
-                            v-for="(item, index) in files"
-                            label
-                            color="blue"
-                            :key="item.filesortedname"
-                            @click="() => downloadFile(index)"
-                        >
-                            {{ item.filename }}
-                        </v-chip>
-                    </v-col>
-                </v-skeleton-loader>
-            </v-container>
-            <v-card-actions>
-                <v-btn @click="downloadAll">
-                    {{ $t("submission.download_all_files") }}
-                </v-btn>
-            </v-card-actions>
-        </v-card-item>
-    </v-card>
+            <v-card-item>
+                <v-card-title>
+                    {{ $t("submission.remarks") }}
+                </v-card-title>
+                <v-card-text v-if="submission.remarks">
+                    {{ submission.remarks }}
+                </v-card-text>
+                <v-card-subtitle v-else>
+                    {{ $t("submission.remarks_empty") }}
+                </v-card-subtitle>
+            </v-card-item>
+            <v-card-item
+                v-if="submission.stderr || submission.stdout || submission.testresults.length"
+            >
+                <v-card-title>{{ $t("submission.docker_test") }}</v-card-title>
+                <v-card-text>
+                    <p v-if="submission.stdout">Stdout: {{ submission.stdout }}</p>
+                    <p v-if="submission.stderr">Sterr: {{ submission.stderr }}</p>
+                    <ul>
+                        <li v-for="result in submission.testresults" :key="result">
+                            <p v-if="result.succeeded" class="text-green">{{ result.value }}</p>
+                            <p v-else class="text-red">{{ result.value }}</p>
+                        </li>
+                    </ul>
+                </v-card-text>
+            </v-card-item>
+            <v-card-item>
+                <v-card-title>
+                    {{ $t("submission.files") }}
+                </v-card-title>
+                <v-card-subtitle>
+                    {{ $t("submission.download_info") }}
+                </v-card-subtitle>
+                <v-container>
+                    <v-alert
+                        v-if="isError"
+                        title="Error"
+                        color="error"
+                        :text="error!.message"
+                    ></v-alert>
+                    <v-skeleton-loader v-else :loading="isLoading" type="card">
+                        <v-col>
+                            <v-chip
+                                class="ma-2"
+                                v-for="(item, index) in files"
+                                label
+                                color="blue"
+                                :key="item.filesortedname"
+                                @click="() => downloadFile(index)"
+                            >
+                                {{ item.filename }}
+                            </v-chip>
+                        </v-col>
+                    </v-skeleton-loader>
+                </v-container>
+                <v-card-actions>
+                    <v-btn @click="downloadAll">
+                        {{ $t("submission.download_all_files") }}
+                    </v-btn>
+                </v-card-actions>
+            </v-card-item>
+        </v-card>
+    </div>
 </template>
 
 <script setup lang="ts">
diff --git a/frontend/src/components/submission/SubmissionTeacherCard.vue b/frontend/src/components/submission/SubmissionTeacherCard.vue
index 94f3702b..9e94b6d0 100644
--- a/frontend/src/components/submission/SubmissionTeacherCard.vue
+++ b/frontend/src/components/submission/SubmissionTeacherCard.vue
@@ -1,7 +1,7 @@
 <template>
-    <v-card class="parent-card">
+    <v-card v-if="!isLoading" class="parent-card">
         <v-card-title>
-            {{ $t("project.group", { number: submission.group_id }) }}
+            {{ $t("project.group", { number: group!.num }) }}
         </v-card-title>
         <SubmissionCard class="ma-3" :submission="submission" :deadline="deadline" />
         <v-divider class="divider" />
@@ -16,13 +16,16 @@
 <script setup lang="ts">
 import SubmissionCard from "@/components/submission/SubmissionCard.vue";
 import { toRefs } from "vue";
+import type Submission from "@/models/Submission";
+import { useGroupQuery } from "@/queries/Group";
 
 const props = defineProps<{
     submission: Submission;
     deadline: Date;
 }>();
-
 const { submission } = toRefs(props);
+
+const { data: group, isLoading } = useGroupQuery(() => submission.value.group_id);
 </script>
 
 <style>
diff --git a/frontend/src/composables/useAcademicYear.ts b/frontend/src/composables/useAcademicYear.ts
index e772df24..460b722f 100644
--- a/frontend/src/composables/useAcademicYear.ts
+++ b/frontend/src/composables/useAcademicYear.ts
@@ -7,8 +7,8 @@ export default function useAcademicYear(): number {
     // If the current date is before September 15, the default selected academic year is the current year.
     // Otherwise, the academic year is the next year.
     if (currentMonth < 8 || (currentMonth === 8 && currentDay < 15)) {
-        return currentYear - 1 - 2000;
+        return currentYear - 1;
     } else {
-        return currentYear - 2000;
+        return currentYear;
     }
 }
diff --git a/frontend/src/queries/Group.ts b/frontend/src/queries/Group.ts
index 0cdbf151..af7badb3 100644
--- a/frontend/src/queries/Group.ts
+++ b/frontend/src/queries/Group.ts
@@ -154,35 +154,14 @@ export function useAddToGroupMutation(): UseMutationReturnType<
     void,
     Error,
     { groupId: number; uid: string },
-    { previousGroup: Group }
+    void
 > {
     const queryClient = useQueryClient();
     return useMutation({
         mutationFn: ({ groupId, uid }) => addToGroup(groupId, uid),
-        onMutate: ({ groupId, uid }) => {
-            const previousGroup = queryClient.getQueryData<Group>(GROUP_QUERY_KEY(groupId));
-            // TODO: this is a placeholder and should be replaced with the
-            // actual user data, but query structure does not support this
-            // currently
-            const newGroup = { ...previousGroup! };
-            newGroup.members.push({
-                uid,
-                given_name: "placeholder",
-                surname: "placeholder",
-                mail: "placeholder",
-                is_teacher: false,
-                is_admin: false,
-            });
-            queryClient.setQueryData<Group>(GROUP_QUERY_KEY(groupId), newGroup);
-            return { previousGroup: previousGroup! };
-        },
         onSuccess: (_, { groupId }) => {
             queryClient.invalidateQueries({ queryKey: GROUP_QUERY_KEY(groupId) });
         },
-        onError: (_, { groupId }, ctx) => {
-            queryClient.setQueryData<Group>(GROUP_QUERY_KEY(groupId), ctx!.previousGroup);
-            alert("Could not join group. Please try again.");
-        },
     });
 }
 
diff --git a/frontend/src/views/CreateProjectView.vue b/frontend/src/views/CreateProjectView.vue
index 211f8b3c..5ed5f619 100644
--- a/frontend/src/views/CreateProjectView.vue
+++ b/frontend/src/views/CreateProjectView.vue
@@ -304,12 +304,12 @@ async function submitForm() {
         } else {
             await createProject(projectData);
         }
-        handleFiles(projectId.value);
+        handleFiles(projectData.project_id);
     } catch (error) {
         console.error("Error during project or group creation or file upload:", error);
         setErrorAlert("An unexpected error occurred. Please try again.");
     }
-    navigateToProject(projectId.value);
+    navigateToProject(projectData.project_id);
 }
 
 function formatProjectData() {
@@ -351,7 +351,6 @@ async function handleGroupCreation(projectId) {
         const groupsToCreate = groups.map((_, i) => ({
             project_id: projectId,
             score: 0,
-            team_name: "Group " + (i + 1),
         }));
         const createdGroups = await createGroupsMutation.mutateAsync({
             projectId: projectId,
@@ -381,7 +380,6 @@ function generateEmptyGroups(projectId: number) {
         emptyGroups.push({
             project_id: projectId,
             score: 0,
-            team_name: `Group ${i + 1}`,
         });
     }
     return emptyGroups;
diff --git a/frontend/src/views/GroupsView.vue b/frontend/src/views/GroupsView.vue
index 140c0061..95cbdda5 100644
--- a/frontend/src/views/GroupsView.vue
+++ b/frontend/src/views/GroupsView.vue
@@ -7,7 +7,7 @@
                 <h2>{{ "Project: " + project!.name }}</h2>
                 <StudentsDialog :students="allStudents" :title="$t('group.all_students')" />
                 <v-divider class="border-opacity-50"></v-divider>
-                <div v-if="groups.length > 0">
+                <v-col v-if="groups.length > 0">
                     <v-row>
                         <v-col cols="7">{{ $t("group.groups") }}</v-col>
                         <v-col cols="2">{{ $t("group.members") }}</v-col>
@@ -22,7 +22,7 @@
                         :isTeacher="isTeacher!"
                         class="group-card"
                     />
-                </div>
+                </v-col>
                 <div v-else>
                     <v-row>
                         <v-col cols="8"> {{ $t("group.not_found2") }}</v-col>
diff --git a/frontend/src/views/SubmissionsTeacherView.vue b/frontend/src/views/SubmissionsTeacherView.vue
index b527bf57..5c6bcda1 100644
--- a/frontend/src/views/SubmissionsTeacherView.vue
+++ b/frontend/src/views/SubmissionsTeacherView.vue
@@ -29,7 +29,7 @@
                     <SubmissionTeacherCard
                         class="ma-3"
                         v-for="submission in submissions"
-                        :key="submission"
+                        :key="submission.id"
                         :submission="submission"
                         :deadline="project.deadline"
                     />
diff --git a/frontend/tests/views/subject/SubjectsView.spec.ts b/frontend/tests/views/subject/SubjectsView.spec.ts
index 151c153f..b3b75f4f 100644
--- a/frontend/tests/views/subject/SubjectsView.spec.ts
+++ b/frontend/tests/views/subject/SubjectsView.spec.ts
@@ -4,7 +4,7 @@ import SubjectsView from "../../../src/views/subject/SubjectsView.vue"
 import {ref} from "vue";
 
 const testSubjectsQuery = {
-    data: ref({as_student: [{id: 1, academic_year: 23}], as_instructor: []}),
+    data: ref({as_student: [{id: 1, academic_year: 2023}], as_instructor: []}),
     isLoading: ref(false),
     isError: ref(true),
     error: ref({as_student: [{id: 1}]}),