You can close currently running apps by following the instruction below.
When an app is open, point to the top-center of the screen.
Drag the app to the bottom of the screen until the app disappears from the screen.
When an app is open, move the cursor to the top-center of the screen until the hand icon appears.
Drag the app to the bottom of the screen until the app disappears from the screen.
Press the Alt key and the F4 key at the same time.