Congrats on finishing the 250 box challenge, you've improved a lot!

One thing I've noticed is you tend to converge your boxes in the wrong direction at times, and sometimes your extension lines are drawn in the wrong direction. Remember, all 3 visible faces of the box should converge away from the viewer, towards the implied vanishing point (which is always opposite to the side the viewer is facing), and your extension lines should always be drawn in the direction of the vanishing point. This link to the challenge page can offer another explanation if you need it: https://drawabox.com/lesson/250boxes/1/wrongdirection

Another thing to remember is that you should never try to redo a line, even if it is clearly inaccurate.

Aside from that, to help with your convergences, refer to this diagram: https://imgur.com/8PqQLE0 and try to think of the entire box as you draw it, instead of just thinking of one line at a time.