Does anyone know any good resources for learning Lua?
(And possibly how to use it with games by Valve (e.g. TF2, GMod, CS:GO)?)

I learnt Lua by watching YT videos, then I joined computercraft servers. Afterward I started using 'Fantasy Consoles', personally I like the TIC-80.

Once you've got a handle on Lua, then try modding the source engine with it.

If you need further assistance, I might be able to help, but try those first. Keep in mind that I have not used Lua in any valve games, so I'm pretty limited there 😥

@coolq thank much