Box size is decent but you could challenge yourself with bigger boxes like the last two you've made. There is room for that. Line extension is good. Dramatic to shallow box ratio is good, but there could be more shallow boxes. With those, you want to avoid parallel convergences since those are considered mistakes. Lines are okay. Just remember confidence>accuracy so they don't wobble.

Boxes are generally varied. Good job with that. Only thing to say is that your Y angles could be a bit more varied. Here's a diagram that might help you with that. Remember, the Y can have any with or angle combination as long as the angles are greater than 90°. Try doing more boxes along the horizon line or facing towards the viewer.

For the back lines/inner corner, they tend to diverge and converge too much, and sometimes it's a byproduct of the outer line convergences. This diagram shows how you can think about the relationships between lines instead of in pairs. Basically, if the inner corner sits closer to the center of the Y, the back line convergence can be parallel to the initial Y. Conversely, if the inner corner sits farther from the center of the Y/closer to one of the tips (usually seen on longer boxes), the back line convergence can be almost parallel to the outer edge of the box. it's okay if you don't understand this right now. It takes a lot of time and practice before it properly sinks in. There's also this diagram which shows how you can change the order in which you draw the lines to get a better understanding of the back line relationships.

Overall solid work. you've improved a great deal over the course of this challenge. I'll mark as complete so you can move onto lesson 2.