Even iOS apps misbehave sometimes – they can crash or stop working any other way, if you’re new to iOS, or have never done this before, you may not know how to actually quit the app (rather than just swiping it off the screen).
Here’s how to terminate an app with iOS 14, according to the verege.
Open the App Switcher by either swiping up from the bottom of the screen and then pausing in the middle, or (if you have a home button) double pressing the home button.
You will see a nested view of all your open applications.
Swipe left or right until you find the app you want to exit.
Swipe up in the app.
Unfortunately, there is no way to close all of your apps at once, if you want to – you’ll simply have to pull them out one by one.
If swiping the app doesn’t solve the problem, turn off your phone by pressing and holding the side button and either volume button until the sliders appear.
Swipe to turn off to the right. (If you have an iPhone with a Home button, press and hold the Side or Sleep/Wake button.)