I didn’t catch that you bought it already damaged.
Add more info about the damage and what you saw or inspected prior to purchase (if you even inspected it).
Also he knowledgeable about what you signed at purchase time.
However, there is a very slim chance that you didn’t buy it “as is.” And an even slimmer chance that anything will be covered by either the dealer or your insurance (0% chance for pre existing damage with insurance).
But on the upside, the nightmare may just be a dishonest dealer and that’s an easy fix if the trailer isn’t all screwed up.