Congratulations on completing the 250 Box Challenge! I can see that you took your time and put a lot of care into your construction. I can also see a lot of improvement being made as you continued through the challenge. Particularly with getting your sets of parallel lines to converge more consistently towards their shared vanishing point. The quality of your mark making also improved by quite a bit towards the end and you do a better job of adding smooth, confident and more seamless weight to your lines as well.

Just to let you know, while working through Drawabox you do not correct any mistakes that are made on any given homework assignment. Just remember that the confidence of the stroke is far and away your top priority. Accuracy is something that you will improve on as you continue working through Drawabox and practice ghosting. It is not your priority while doing these lessons. So just keep that in mind going forward.

One thing that stands out to me about your work here is that your boxes are rather small. In the instructions you are told to stick to 5-6 boxes per page (assuming you're working with the recommended A4, 8.5"x11" sheets of paper), so that you will have room to draw your boxes at a reasonable size. One of the reasons for this is because drawing bigger helps engage your brain's spatial reasoning skills, whereas drawing smaller impedes them. That being said, you did show a lot of improvement in your boxes. So I recommend that you simply start creating bigger (not huge, just bigger) boxes in your warm-ups in the future to help you develop your skills even further.

Finally while your convergences do improve overall I think this diagram will help you further develop that skill as you continue through Drawabox. So, when you are looking at your sets of lines you want to be focusing only on the lines that share a vanishing point. This does not include lines that share a corner or a plane, only lines that converge towards the same vanishing point. Now when you think of those lines, including those that have not been drawn, you can think about the angles from which they leave the vanishing point. Usually the middle lines have a small angle between them, and this angle will become negligible by the time they reach the box. This can serve as a useful hint.

You did really well on this challenge, good luck with lesson 2!