Garry's Mod run faster

Hello. I have question. Is possible to run gmod on DX7? or increase fps on DX8? Thanks

To be frank if you’re having performance issues when running it in DirectX 8 mode you aren’t going to gain anything at all by changing settings.

I hate to be that guy, but you really need to upgrade your PC if it’s struggling with a Source Engine game.

Warning:
Our games no longer support DirectX 7 as a launch option. Using this can cause crashes. If you are using -dxlevel 70 make sure to remove it from your launch options.

From steam support