These are looking better, 2, 3 and 6 in particular. Only thing I'd like to point out is that box 1 has the top face hidden, like it happens in 2 point perspective. This doesn't normally happen to rectangular boxes in 3 point perspective since it's the perspective of an object with all of its faces oriented at an angle with respect to our line of sight (by contrast, in 1 point we are observing the boxes with their "depth lines" parallel to our line of sight and both verticals and horizontals perpendicular to it, while in 2 point we are in the same situation as in 1 point, but with the box rotated around a vertical axis). I advise you to keep exercising in your warmup routines on box-related exercise. Slowly but surely, you will see improvement. As a last line of advice, I will drop here one of my other critiques where I give some tips on how to improve your back corners (the method I use is illustrated in the replies): https://drawabox.com/community/submission/87XZS5GL

That being said, I'll go on and mark your lesson as complete. Hope you will have some fun with lesson 2. Good luck and good work!