take some basic script, for example River Shell, and do actions in game, compare actions with code, locate those actions in code, and see what does they do.
But firstly you'll need to learn syntax. Pawn, use SAMP wiki for that
My tip to you is to start off with making a basic TDM gamemode. Learn how you can add vehicles, classes, spawns and weapons. After that, try to make some simple commands and then you'll learn the rest.