Hi there!

your lines are quite good in general and drawn with confidence... some are a little arching (but really imperceptible) so it's not a problem... But I can see especially in the planes and the boxes that you tend to be a little scarce, finishing the line before your point...

The ellipses have a good ellipse-y shape and not wobbly, drawn through not too many times... I can see though that some time are overlapping with each other, or maybe they doesn't "fit fight" in the planes (too big or too small) at times... (and as said before the lines are too short at times)

In the rough perspective you got the idea right, but here too you're not ghosting enough and the boxes have lines too short and not connecting at all almost everywhere...

With the rotating boxes I can see you had problems with the bases... they're definitely not consistent in sizes (they vary too much) and spaces, and having ao much depth really didn't helped you (you get smaller bases and it's more difficult to go from there)...