How do I close an App fifer rent from the “Force App to Close?

While trying to remedy my inability to hang up the at the end of my conversation on a phone call. (Still trying to find that answer). An Apple employee (Sterling) had a hyper text to explain how to force the phone app to close. It directs the bottom to middle of page swipe. That’s the ONLY WAY I know. So I’m trying to find if there is any other way to close an app.? And BTW if you know how to fix phone calls the caller can’t hang up from. Unless you wait until the call recipient hangs up (and of course they can only hang up if he/she doesn’t have a friggin’’ iPhone)!