Remove split screen on Facebook

To transform a Slide Over view, to Split Screen, use the grey drag-bar at the top of the Slide Over Window; drag downwards and to towards the side of the screen. As the view changes, lift your finger. Done.

It’s also worth noting that you can easily change a Slide Over to Full Screen view in a similar way. This time, using the same drag-bar, drag to the top-centre of the screen, then release.

You may find these overview Apple video guides to be helpful:

After viewing, you’ll be ready for the additional Multitasking Guide:

https://support.apple.com/en-us/HT207582

The iPad User Guide for iPadOS is also a rich source of information. Here are links to both the downloadable and online versions of the Guide:

https://help.apple.com/epub/ipad/en/

https://support.apple.com/guide/ipad/welcome/ipados

I hope this explanation and additional information is helpful in resolving any difficulties you may be having with Multitasking features of your iPad.