Since you have programming experience getting started shouldn't be too difficult for you. You can jump straight into the introduction in the docs or just jump straight into the your first game section. It gives you a quick intro and tells you how to get around.
After that you can check out the ultimate introduction to Godot 4 video. It's a massive 11 hour video that teaches you almost everything you need to know (in 2D game development). Good luck.
Fiiiinally some good news on GameMaker. I honestly don't know what they were thinking with a subscription just to use the engine, their main audience is indie devs that are just starting out so they just chased them away to engines that are free to use like Godot, Unity, Unreal, etc. You can't even export web games in Gamemaker for free unless you upload it to Opera's website.
I briefly used gamemaker 2 and it was a pretty good, polished engine. Shame Opera sabotaged it so much. It was becoming clear that Godot was quickly taking its users, so the timing of this announcement is good.