That geometry is super messy and bad. But at least is just three problematic parts that look very easy to solve. You have a lot of overlapping faces so it’s just a matter of making them not overlap. You could try selecting the vertices and double tap G to slide them out of the way. At least it looks as if that is possible, you’d have to try and see. Also there might be interior faces so switch to face selection mode and see if you have very squashed faces where you’d think there’s an edge there.
