How do i unify imported parts with surfaces?
I am new to 3d modeling and, now, I am wondering to make a control for our robots. I participate in Warthog Robotics here in Brasil, one group of USP (University of de São Paulo) and we need to make this control based on Dualshock 4 V2. But we need to change the dimensions to place our electronics. I found one 3d model here at grab cad, and this model is impossible to edit on it, so I am doing some cuts and making surfaces, cut and surface... Sorry for my terrible English, but can you help me?
Attached I sent a part of the model...