AutoCad :: How To Trim Large Amounts Of Polylines

I am finishing up the exterior design of a building which consists out of metal plating which should be laser cut with a pattern. Now I drew the lines for the laser cutter as a template which will fit the pattern into the contours of the exterior design. Only problem which occurs is that my pattern, which I have group to easily copy, creates very slow desktop performance.

How to I external trim all the groups at once because it does not seem to do this. I can´t attach the cad-file because manager won´t let me. but it trimmed some of the group but not all the lines in them. How is this possible? I've tried blocks but they don't clip either.