GMAT will try to get you caught up in trying to understand the details of very technical passages - you don't need to do that.
Try to pick out the author's main points, conclusions, tone, scope, etc., without necessarily understanding every sentence in the passage.
The GMAT does this purposely, of course, to test your patience, concentration, and focus. So, in a way, you just have to deal with it. But the above suggestion should help you to approach it in a different way.