Hey there Vladyslav, congratulations on completing the 250 box challenge. It is no small feat so you should feel proud! Let's get looking at your boxes.

So at the start of your challenge, you were struggling with things like making your lines converge instead of diverge, but through practice and proper application of your extension lines you have shown considerable growth and by the end of the challenge your boxes feel much more solid and convincing. You are still having some issues getting all of your lines to converge consistently with respect to one another - sometimes your lines are still parallel or even diverging, and other times you have two points of convergence for a parallel set instead of the expected one point. Regarding the first point, that is a matter of being mindful with your lines and practice drawing more boxes with far off vanishing points. It's great that you are practicing the more difficult subtly converging boxes, and it for sure takes practice but you'll get it! Regarding the second point, this often occurs when we are not looking at our parallel lines as an ensemble, but rather focusing on one plane at a time. As Uncomfortable explains in this infographic all of the parallel lines are related to one another by the vanishing point and the location of the vanishing point determines the angles between the parallel lines. Often times beginners will draw the first plane of their box, making sure everything is nice and convergent and neat and then move on to the next plane doing the same thing, but with no regard to the first set of lines they put down. This is why we often end up with thsoe two points of convergence such as in box 249. The key is to "step back" so to speak and look at and draw all the lines with consideration to their family members (the other parallel lines sharing a vanishing point) and then as you draw them their convergences will fall more into place.

One more thing I would like to touch on is your line weight. You are doing a good job applying it neatly around the silhouette, but it's still a little heavy on the interior lines. Just something to keep in mind to help further the illusion of solidity in your boxes!