It's good to have pull request templates. It helps whoever is opening the PR if everything is ok. For example, updating documentation, tests, etc.
As the commit, you don't explain what you did. You can use the commit message here. But you can provide extra information, like videos, screenshots for the current and new, links, etc.
It's not mandatory to open one pull request to the feature. You can open several when it makes sense. When you have a lot of changes, it's harder to review. So, try to split and make your pull request more readable.
The code review it’s not related to what you like, it’s related to the practices that are followed in the project or the best practices that we should follow. It’s not personal.
When someone asks for improvements, they want to make life easier to maintain the project in the future.
Explain what is missing and how it could be improved. The problems of the current approach.
You can test your suggestion before instead of asking to the requester test it.