There is a zoom functionality on the iPad that may confuse users sometimes. You may end up in a spot where you zoomed in way too much and the screen is way too big, making the device unusable.
This is all part of the Zoom setting under General > Accessibility > Zoom. It enables you to zoom in and out by double-tapping the screen with 3 fingers. So if your screen is stuck where it’s big, just try double-tapping with 3 fingers to get out of this mode. You can also try dragging 3 fingers down on the screen to decrease magnification.