I accidentally make this menu put in the backward. how to reset it?

I accidentally made this menu bar disappear. I think it is put in the backward because I totally can see it through. I don't know to reset it.

• no it is not. i'm 100% sure it was just my mistake when drag and drop new window. because when i open the new file it resets to the default setting. May 17 at 15:04

Un-tick the box that says "Region Overlap" under Preferences > Interface: