1993 bmw-m clone

I bought a 93 bmw coupe. It is bottoming out as well as has a slight shimmy when going 35 mph and under. At 60 it humms. Shifts great. It is a little squeaky on bad roads. I think it may be needing a tire balance and rotation. If it was lowered too low when they did the m conversion kit, could shocks be an issue with the squeaking. Any ideas for when it goes to the shop. Also the drivers window has to be rapidly clicked to go down, what could be causing that sticking?