Apps you install from the Windows Store don’t slow down your PC, so you don’t need to close them. When you’re not using an app, Windows will leave it running in the background and then close it eventually if you don’ t use it.
But if you want to close an app and remove it from view, drag the app to the bottom of the screen.
To completely stop all processes associated with an app, drag the app to the bottom of the screen, and hold it there until the app flips over.
It’s still a good idea to close desktop apps when you're done using them, particularly before shutting down your PC.