A program that stops a process when the focused window is in fullsceen. If the focus switches to a non fullscreen window, the stopped process is started again.
Open the .sln file in Visual Studio 2019 and build the FullsreenDetectorGUI Project.
Just run the exe, select a process form the list, that you want to stop/restart when another app goes in/out of fullscreen. In addition you can enable autostart. Then click Ok and the app runs in the background. You can open the settings again on the Trayicon context menu.