Hello, congrats on finishing the challenge. I'll be taking a look at your work today. So after a quick look through this is a pretty great submission and frankly since you've followed the directions so well you've almost critiqued yourself so it makes my job pretty easy here. I do have a few things for you to think about though.

So starting off you did a great job extending your lines back on your boxes here and checking you work. You even caught yourself when you extended the lines in the wrong direction too so that's great. You already have a very clear idea on how vanishing points and convergences for boxes work in 3 point perspective. Still please check this graphic as it's always helpful to think about these things. https://i.imgur.com/8PqQLE0.png You are still running into slight convergence issues but your boxes are getting pretty solid overall and the improvement you see on them is going to be much more gradual at this point.

However I am noticing a bit of a worrying trend and it's still occuring in your later boxes. You seem to be either not ghosting enough or have fell back into drawing from your wrist for shorter lines and it's causing a consider amount of wobble in your linework. My biggest advice to you after looking this is over is to make sure you are ALWAYS ghosting your lines even if they are pretty short. The only time you don't really need to ghost is when you are doing the texture exercises in lesson 2. Otherwise, every single line, circle, ellipse, etc you put down for these lessons should be ghosted and drawn from the shoulder if possible.

So your boxes are on the right track and of course they could still use some more work and will for a long time so keep up with the practice. This was a fantastic submission though and your self critique is the exact type of mentality you need to have while learning how to draw. I'm going to mark this as complete and good luck with lesson 2.