i assume you are talking about those stair like bench like steps in the 2nd picture. after deleting the fillets use ExtendSrf then trim the overlapping parts off. or you use the curves which are available from the edges or draw them quickly and use EdgeSrf. there are probably plenty ways to reconstruct it quickly without having to unrim.
if you cant get further just cut out a square piece of your model and drop the file into the reply field then somebody can show you.