How to combine many sections of imported surface to one?

I have an imported part (parasolid) that has several asymmetric surfaces that are really slowing down the processes I need to perform with this part. I have tried to create a new surface using the convert entities sketch tool converting the longest sections of the curves and then adding a partial ellipse or a parabola but niether fit quite right. I end up with some of the new surface and some of the old surface exposed. Is there a way to combine the small sections of the imported surfaces, or to change the import settings so that the curve is continuous? Preferably something that speeds up the manipulations of the part.

SolidworksSurfacing