I used some courses on Udemy called something like design for 3d printing with Fusion and it went through starting with very simple flat objects(I think it was

I used some courses on Udemy called something like design for 3d printing with Fusion and it went through starting with very simple flat objects(I think it was a comb) and working your way up then there were intermediate and advanced courses for after. I went from zero understanding of fusion to being not an expert or even advanced but comfortable enough to design pretty much any little part or idea I have in just a few days of practice.