Some users download third-party task manager apps to manage their apps for them. When not managed properly, these task managers may actually do more harm than good. If you have one of these apps installed, it's recommended to uninstall it unless you are very much aware of how the app runs and manages system tasks in the background.
A simple yet more efficient way of ending running apps is closing them from the
Recent apps screen.
Flip through the cards to find the app, and then swipe it left or right.
To close all running apps at once, tap