I can't play Garry's Mod

I open up Garry’s Mod, it loads up slowly, It shows me the Menu screen and Crashes but I can move the Mouse.
How do I fix this? I tried to redownload the game after it was crashing I think because I had alot of addons. And I’ve already tried to Verify integrity of the game caches

I assume by “had” being past-tense you removed the addons and the problem is still there? If you haven’t removed the addons, then do that, make sure both the addons folder and workshop subscriptions are empty. I think Steam has an option for defragmenting game files, do that as that can cause things to load slowly