If you're not careful, your Android smartphone can run a lot of apps at once. That can cause problems like the phone acting slow or draining battery quickly. Fortunately, you can close apps easily from within the multitasking interface. The exact process varies a little depending on your phone model and manufacturer, but it's usually something like this: Swipe up from the bottom of the screen (if you use gesture navigation) or tap the recent apps button (if you have three-button or physical home button navigation). You should see a list of apps currently running on your device.
You can swipe them away or tap a button that says Clear all, X, or a similar one. This will close all apps that are still running in the background. Occasionally, you may need to force close apps on your samsung s21 for various reasons. For example, if an app won't shut down or it keeps glitching, you can try to force-close the app and then restart your device.
If an app is slowing your device or draining its battery, you can try to speed it up by clearing its cache and data files. Note that deleting these files can cause the app to take longer to open next time you use it. It's recommended that you back up your phone before doing this so that you don't lose any important information.
Another way to speed up an app is to disable its auto-optimization feature. These features are meant to improve performance while you're using the app, but they can also lead to issues when you're not using it. You can find this option in the settings menu of your Samsung Galaxy S21.