Hey there, I'll try to give you some feedback on your boxes:

  • Your hatching looks clean, nice accuracy on that

  • Overall you boxes appear to be very small, you could try to draw bigger boxes, so they take more space on the page

  • most of your lines appear to be parallel or even diverging, drawing bigger boxes and choosing vanishing points closer to your boxes, maybe even somewhere on the page can help with that

  • the extended lines to you did to check your lines are a little bit hard to see, doing stronger marks on those would make seeing where you went wrong easier

  • choosing points where two edges meet with a dot and then ghosting both to see if they are right could help you along way. Course correcting and moving the final dot for your ghosted line slighty before actually drawing it can improve your boxes and perspective. Here is an example of the method https://imgur.com/3zoQA65

  • Your lines are fairly straight, but there is some degree of wobble, try plottingg your lines with dots and ghosting your lines from your shoulder

  • I always recommend hatching in the planes that covers the inner corner to make your boxes' perspective read better