Heyho Danilo!
You did a great job on the anatomy assignement!
As far as I can tell, most of it is correct and in alignement with what Marc teaches.
Just a quick note from my side: The insertion points of the deltoids and the gluteus maximus seem a little off to me: the delts insert more laterally on the humerus (in your earlier sketch it was actually correct, but it seems as if you move it more to the medial side of the humerus) and I personally would make the gluteus maximus wrap around the leg a little more and move the insertion point to the lateral thigh.
What has helped me the most (apart from having learned all this stuff in university
) is to study real anatomy charts like this one:

With these charts you can identify really well where the muscle actually attaches at the skeleton!
Good luck and keep up the great work, man! 