An app is behaving weirdly. What should I do to fix it?

Close the app using File > Quit, Cmd-Q, or if necessary force–quit (see below). Open it again. If it’s still not okay, check its menus, the App Store or its website for updates to install. Install any updates to macOS (in Catalina’s System Preferences, or in App Store > Updates. Restart your Mac and open the app. Still not okay? In the Finder, go to ~/ Library/ Preferences and drag anything named after that app to the Trash. If it works, you may lose some settings.