@Eric Van Den Top said
move that bar up and down?
The area above the yellow line in your image is where Outlook puts All Day Events. This space should expand/shrink automatically based on how many All Days you have in the week. You can't adjust it manually. Looks like yours has gotten "stuck".
Try resetting the View.
View -> View Settings -> [Reset Current View]
If that doesn't work, come back and we'll look for something else. e.g. "Hidden" All Day events.