Go into your apps list from your settings, and make sure you have no 'Easy Home' or odd email widget apps downloaded. These often time are given permission to overlay everything else happening on your device, so just make sure you don't have any of that going on. If there are any odd games or cleaner apps you didn't personally install, delete them.
Also in your settings under apps, go to 'Default Apps,' and make sure you're using One UI for your Home App.
