Black screen when playing Garry's Mod

Hi @Piskojuy, and welcome!

As frustrating as that I imagine that is for you, I’m going to have to tell you we need more information for there to be a chance to figure out what’s going on. To that end, see [HowTo] Provide System Information, [HowTo] post screenshots and links and [HowTo] Increase your chances of solving your issue.

Hope you manage!