Thank you a lot for your fast and complete review ! I'll work on my ellipses through warmups and try not to overlineweight next time. As for the perpendicular/parallelism, I understand what you've said and I tried to, but ss we had to draw without a ruler, it was my estimation of parallelism and perpendicularity that was a bit wrong, and I don't know how to improve that freehand (except through more practice experience).

Now is the time for the boxes marathon ahah