Some advice

I try to create a mod for gmod can you help me how to do it?

Boy, you got a lot to learn.. You will need to learn lua then proceed onto gLua. Code Blue has a really good Youtube Tutorial Series on his channel that teach you most of these things, it's really not something you can learn within a day. This will take LOTS of time.

Lua Series: https://www.youtube.com/watch?v=RoERwONu...N2ZkRQBfrZ
gLua Series: https://www.youtube.com/watch?v=c1mQ3mpd...p9jyNSTIo_

You enjoy :D

One of my best recommendations is to learn how to code if you haven't already. Afterwards it's best to look at the source code of other mods and pick apart best practices for urself.