I have two machines here, one MacPro 8-Core from 2009 with Quadro4000 and 2 Gig and a brandnew PC i7 6-Core with GTX980 and 4 Gig.
I thought switiching from this old Mac to a brandnew PC would make my projects a lot faster but with newest realease of AE I can not see any improvements?!
What am I doing wrong?
If you use the ray-traced renderer, the difference is that the GTX980 won't work to accelerate it (until the next update for AE comes out later this year). You shouldn't use the ray-traced renderer anyway, it's considered an obsolete workflow.
If that's not it, we're going to need some more information about your contents of your composition and the hardware of the two computers.