You have clearly managed to enable a Slide Over view - this being a major multitasking feature of iPadOS, fully detailed in the iPad User Guide for iPadOS.
Here is the easy way to change the Slide Over view, to full screen...
Identify the small grey drag-bar at top-centre of the Slide Over window. Touch-and-drag the drag-bar to the top-centre of the screen - and lift your finger; the Slide Over window will transform into a full screen view.
You may find these overview Apple video guides to be helpful:
After viewing, you’ll be ready for the additional Multitasking Guide:
You have clearly managed to enable a Slide Over view - this being a major multitasking feature of iPadOS, fully detailed in the iPad User Guide for iPadOS.
Here is the easy way to change the Slide Over view, to full screen...
Identify the small grey drag-bar at top-centre of the Slide Over window. Touch-and-drag the drag-bar to the top-centre of the screen - and lift your finger; the Slide Over window will transform into a full screen view.
You may find these overview Apple video guides to be helpful:
After viewing, you’ll be ready for the additional Multitasking Guide: