I have checked it and it's great progress! The results are smoother, especially on the ellipses is where I can see the awesome improvement. Although is not perfect and you need more practice, I think you got the point.

Your rotated boxes are better now. They still have errors to point out like the corners being too visible. They should be almost covered because of the rotation they should have to give the illusion of a 3D sphere. Also, there are boxes whose back faces are not wrapping the imaginary ball that is in the inside of the structure.

You still have to work on your lines because they feel not as smooth and straight as they should. Maybe increasing the speed could help but you have time to find out in the 250 box challenge.

I think you are ready now to move on. I think you have not mastered the fundamentals enough but the 250 boxes are a long challenge to finish and you will have time to practice. I recommend you to make only a couple pages of the challenge each day to let your brain sink the experience slowly. The majority of the progress happens while we sleep, take that in mind.

Also, warm up with the exercise you had trouble with. Practice the smoothness of your lines and remember to prioritize line quality over accuracy.

I wish you luck in your journey. Don't let that boxes defeat you ;) !