Hey there, congratulations on making it through the box challenge, it's a bit of slog, but it's a worthwhile one.

Your lines are generally confident throughout and it's good to see you've consistently and carefully applied hatching to all your boxes, as well as the check lines. You've drawn a good variety of extreme and more shallow foreshortening, which is good to see as well. Generally we suggest that students limit their boxes to 2-6 per page, as this gives them lots of space to work through the spatial problems they'll face.

In terms of your convergences, these generally trend better as you go however even on your final page, there's some pretty obvious divergence that suggests you still may not be thinking about your boxes in terms of how their angles relate to one another. We share this diagram with students upon completion of the box challenge. Basically what this shows is the consistent pattern of how the angles of our lines relate to one another - these rules apply to any kind of box. The green and orange lines are so close in angle so as to be almost parallel whilst the outer lines (blue and magenta) will converge at a slightly sharper angle. This rule becomes slightly more subtle when you're doing boxes with shallower foreshortening but it does still apply.

Overall, you've improved quite a bit and as long as you keep boxes in your warm-ups with the above in mind, I do believe you will continue to improve.

Finally, I'll address your questions. Regarding the line weight, generally it's better to apply this after you have drawn the box as it's quite easy to end up reinforcing the wrong lines if you do it as you go. I did notice a few of yours were not particularly confident, so make sure you're ghosting out the line weight you're applying - if it's slightly off, this isn't a problem because it can usually still do its job if it's "close enough".

Also it´s funny that a lot of them looked correctly, until I actually corrected them. I hope I´m not alone with this.

This is entirely normal and is exactly the purpose of applying the check lines as only certain mistakes become obvious once you do this.