The gun, from modelling and texturing point of view, looks just fine to me.
That said, the weird combination of box and drum magazine must be one of the fugliest in the history of firearms. (Yes, I know, it was made for Luger P08 and the box part had to fit within the pistol's handle, but with MP18 the entire assembly is outside the weapon which is like sticking a thumb in a sore eye.)