How to customize DarkRP menu?

I want to learn how to customize the DarkRP menu i looked in the VGUI file and it seems pretty confusing to me.

What should i learn to be able to do this?
Where do i start?
How long does this take to learn?

I don’t have that much experience with lua the only thing that i really did was customize printers for DarkRP.

I would try learning to make basic menus to start. I’m not the best at VGUI but I would consider using the gmod wiki to start.