In reply to Archimidis.

I would begin on the theme side of things since you do theme development too. One of the best places to start is Carolina Nymark's Full Site Editing course. It's free, and Carolina is one of the most knowledgeable people in the theme space that I know. Lots of great info on that site.

Marcus Kazmierczak's Copyright Block helped me learn how to build my first block type. It's written in vanilla JS, so it was easier for me to just get over that initial hump of getting my first code into a working state.