Yeah, i'd also suggest using the gamemaker official PDF tutorials, if you go trough all of them, then you could call yourself and advanced gamemaker "game maker"
And btw, CoolGamer 48, gamemaker wasn't bought by yoyo games, what happens was this:
the creator used gamamaker under the license of the university where he worked for, but because it became a profit making business, the university didn't let him publish it under his name (don't know the reasons) so he started his own company and sells keys for gamamaker.
What i want to say is that YoYo-Games is the propperty of the creator of GameMaker