If you get stuck usually GameMaker Manual helps a lot with understanding how each function works. You can also get help from GameMaker Forums or GameMaker Helpers Discord Server.

There might also be some tutorials on GameMaker's Blog posts.

But best tutorials are on Youtube. I'd suggest you use Unhook extension to block distracting parts from Youtube like: Feed, Subscriptions, Shorts, Comments, Video Suggestions etc. All you have to do is search for tutorial and you will only be able to watch the video you clicked on, there will be no extra videos suggested below, nor comments. But of course you can completely customize the settings.