Links in email open only 1/3 way. This is NOT the split screen issue. To get rid of this, I have to completely get out of my email. Someone else asked the same question and never really received an answer
iPad Pro 11-inch Wi-Fi
You perhaps have a Slide-Over view enabled, this being a feature of iPadOS.
The easiest way to switch from Slide Over to a full-screen window is to touch-and-hold the small drag-bar at the top of the Slide Over Window, drag to the top-centre of the screen - then release; this window will become full screen.
Here is an Apple video that demonstrates use of Slide Over:
... and the corresponding page from the online version of the iPad User Guide for iPadOS:
https://support.apple.com/en-gb/guide/ipad/ipadfe7c65e9/ipados
... and a further help page that describes many associated features of iPad multi-tasking:
https://support.apple.com/en-gb/HT207582
I hope this information os helpful is resolving your immediate question - and in providing useful references to significant functionality.
Links in email only open 1/3 of the way
