exit split screen

Take the black bar in the middle and slide it in the direction of the app that you want to close so if you have mail on the left and safari on the right. If you wanted to close mail and leave safari open, grab the bar, and slide it to the left to close mail and safari will take up the entire screen.

See the middle barrier drag it holding on the barrier to the left or right depending on what app you want to use

Hello,

Please refer to the following Apple Support video.

How to multitask with Split View on your iPad — Apple Support