how was the wooden door attached at the top?? there is no door frame? you need to have a proper frame/jamb

you make it level by adding braces above the top portion.

Time to take the door out and put a proper frame in the way Beth's pictures show. Then put your walls in. Then re-install the door.

well that's quite a jimmie-rig. yeah, you need a proper door frame. or, just do what you had. up to you if you want it weather proof.