I have an wall object with z = 2915m ! I can display this strange dimensions with scale cage. When I reduce the scale cage, my wall is going to be very thin. How can I reduce the 2915m dimensions and keep my wall width. Here is my file My file.
I don't know how you managed to do that, but here's how to fix it:
Go into edit mode. Set the view mode to wireframe. Use box select to select the visible vertices, the ones that belong to the arc and you want to keep.
Press CTRL I to invert your selection
Press X and delete vertices.