You can force an app to close in a few swipes if it hangs or malfunctions on your iPhone SE. There are times when you may need to do this even though it is not normally necessary. Here’s how.

Normally, You Don’t Need to Close Apps.
In general, you don’t need to force an iPhone app to close unless malfunctioning. As a result, the iPhone operating system (iOS) manages system resources automatically. If you do this frequently, your iPhone may slow down.
Unfortunately, apps sometimes freeze, hang, or misbehave. You can force an app to close in those cases. You will have to force the app to reload completely when relaunching it, which may fix any temporary issues caused by bugs.
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How to Force an App to Close on iPhone SE
It would help if you launched the app switcher to close an app on an iPhone SE. You can switch between open apps with the app switcher, which also can close them.
Your iPhone SE’s home button must be pressed twice quickly to open the app switcher. Click the large circular button below the screen twice quickly to access the app switcher.
If you do it correctly, you will see images displaying the apps you currently have open (or suspended) on your iPhone SE.
Swipe your finger left and right through its thumbnails until it appears in the list to close an app. Fingers can be used to flick the app’s thumbnail upward (toward the top of the screen).
You will be forced to close the app when the thumbnail disappears. Using this method, you can close as many apps as you want, but remember that it isn’t necessary to close them all unless one is malfunctioning.
After relaunching an app, update the app from the App Store if the problem persists. Another temporary fix is to restart your iPhone SE. See if an iPhone system update is available to fix larger bugs. Good luck!