Super glad You enjoyed it so much! ^^
When it comes to learning Godot I'm self-taught, (That is I just messed around the engine trying out random things and reading the documentation on any roadblocks), but 2 channels that I really like when it comes to the tutorials for cerain systems and tricks in the engine are Gwizz and Queble!
As for my own advice: In my opinion the best way to learn Godot is to just stick to one (although simple) project that you know how you want everything to look in, and stubbornly try to create at least a few systems that resemble your vision.
Since you've created games in GameMaker, you could try to recreate one 1:1 in Godot just to see how the workflow looks like, what you like and what you don't like. Good Luck!!