First of all, you're grinding a lot. Completing the box challenge in 5 days is doing it too fast. You should take your time with each box, and remember that half of the time you spend on drawabox should be spent on drawing for fun.

You've mostly worked big, which is very good, and your lines and convergences do improve, though there are a few issues with your convergences.

First one is that you have some clear convergences. As I show here), lines should never diverge, they should always get closer, even if it's only a bit. And these divergences you have are ones you can fix with a bit of thinking. Before drawing the lines, think if the line you are going to make will go away or get closer to the line. You can use ghosting to check this. Don't draw the line until you are sure it will not diverge.

You also still have divergences on your inner corners, I recommend trying this order of drawing boxes, and see if it helps.

Your boxes are also pretty similar. You haven't been practicing different kinds of boxes. So I recommend using this Y generator for your next boxes on your warmups, so you can keep practicing different kinds of boxes.

You've also not drawn extreme perspective boxes, so I recommend working on them on them as well, they are less common than shallow perspective ones, but they are still common.