How hard is to code?

I find that coding is more of an exercise in thinking rather than learning/remembering what code does what. Once you memorize the basics of a coding language and get into the right mindset for problem-solving, it just comes down too time. LUA isnt a bad option to choose, unless the reason you are choosing it is too learn roblox development :/
If your starting out, dont try roblox development, make basic java programs (Preferably ones that you can use eventually, autoclickers, screen recorders are an interesting challenge, etc). With roblox development you need to have server-sided scripts, test things to make sure your scripts arent only working locally, etc.