is it so hard to learn .lua ?

Is it hard to learn .lua to customize your server (Jobs, entities etc)? - Absolutely not

You can even find script makers online that will help you insert information, then they'll just drop a code for it if you really find it hard to set up your Lua files for server.

Is it hard to learn .lua for creation of scripts? -Well, it highly depends on you and your wish to learn it. Loads of tutorials on youtube to get you started. I'm sure you'll handle it