There's a thing with a 2x4 across the middle of the door (from jamb to jamb).
Push the door against the lumber then press on the top and bottom (2 people ?)
til you get it back in shape.
There'll be someone jumping in here with a better explanation, I'm sure.
But, if not, this is a starting place...
28' Safari SO
Excursion 6.0 4x