1st - The Godot Docs - read the manual is the best thing ever.
2nd - In the Project Manager, when you start Godot, go to Asset Library Projects and install some assets and look how they work.
Create a new project and toy with the asset project to see what happens.
3rd - Youtube:
ExtraCredits : Minimum Viable Product; Basics How Start Your Game Development
Godot Tutorials
GDQuest
Kids Can Code