Crash issue on my mac computer.

Hello, I have been experiencing crashes for about 4 years now on my iMac (21.5-inch, Late 2012).

The common crash that I have been getting is, I log into a darkrp server then I can get about 10-30 minutes of gameplay in then suddenly it crashes!

But lately I have been experiencing some other crashes while connecting to the darkrp server that I always play on, during the sending client info page, it freezes and closes randomly to desktop.
^This glitch happened after deleting GarrysMod folder and deleting local content in a hope to fix the original crash issue.

So now I have to fix the sending client info crash and the random crashes after 20-30 minute gameplay!
I have tried -dxlevel 95 in console as I saw from a youtube video, but it doesn’t work.

^ One of the crash reports I get when I click send to apple. ^
iMac Late 2012 (desktop)
Memory 8 GB 1600 MHz DDR3
Graphics NVIDIA GeForce GT 360M 512 MB
Processor 2.7 GHz Intel Core i5

Thanks ~Tim_27

**Any help would be GREATLY appreciated **
Don’t even bother commenting about how I should get a windows computer ;-;