Hope you got ‘er real cheap because that is as crooked as a dogs hind leg.
Only 2 ways to fix that is if you can reach it from tearing apart the insides to get to it or wiz wheel it open form the outside and do some real fiberglass work afterwards, IMO.
The bigger question is I understand why you have it jacked way up with no support under the belly AND walking around inside it? Are you testing the ultimate strength of that bent/rotten corner to see what it takes to make it collapse?
I know you had to jack it up within an inch of its life to get it off that lifted truck, but may want to exercise a little caution in stability or your next step will be loading it back into the truck with a reach fork and some straps to haul to the garbage dump.