How do you close all apps running in the background?

Tap and hold on the application and swipe it to the right.

This should kill the process from running and free up some RAM. If you want to close everything, press the “Clear All” button if its available to you.

How do I force quit all apps on Android?

Go to settings on your phone > apps (applications) > then choose the app you want to force stop. Then, there will be a button that allows you to fully close the app. How do I restart an app after a force stop?