Gmod Crash on iMac

Hello guys!
First, i want to say that im very new here. I never used Steam before and Gmod is my first game here.
So i payed, downloaded and started Gmod. I starte new game and choosed a random map and clicked on play.
So what happens is that it loads for a few minutes and the gmod logo appears. Then, it just crashs with this error log:

My iMac Specs:
iMac late 2009
2,66 GHz Intel Core 2 Duo
NVIDIA Geforce 9400 256MB
Mac OS X Lion 10.7

FYI that Mac barely reaches minimum requirements to run the game with OS version and graphics card.

Thank you for the Information, but it doesnt really help me.

Does anyone have an idea?

Don’t buy a mac

EDIT : Don’t game on it, too

He obviously gave you the reason why you are crashing. Close thread?