How to force quit apps on an iPhone  💥
You don't quit an app when you close it on your iPhone/iPad and return to the Home screen. It's still running in background. It's like "pausing" an app. Force quitting an app is the best choice if it crashes, becomes stuck, or is acting badly. The app will close and then load up again. You should now be able to fix any temporary problems you had with the app.
The best way to force quit an app on your iPhone
You can open the App Switcher or force quit an app on your iPhone using different methods depending on what model you have and what version of iOS. First, let's discuss the older iPhones (XS, XS Max and XR) that have the notch at their tops but no Home button.
You can either stay in the problematic app on your iPhone or open the one that you wish to force quit. Swipe down from the bottom (the "Home bar") of the iPhone-screen.
Now as you move towards the middle of your screen, hold your finger on it. To open the App Switcher, lift your finger when you see the app's preview in card size. To view all previously opened apps, you can scroll horizontally within this interface. Swipe up on the preview of the app that you wish to close. The card should disappear from the top of your display.
You can quit iOS 11-running iPhone X by tapping and holding the app preview. Then you tap the red colored minus sign button to be able to quit the app. If your iPhone has a physical Home button you can double-press it and open the App Switcher. Next, swipe up on an app preview to close that app.