Congratulations for your first lesson!

? can suggest some tips.You need to draw your lines in one stroke and without blocking your arm even it's not looking like the points you put joined. i can suggest you to exercise the ghosting method. its absolutely gonna improve your box shapes and you see less point you cannot joined. Finally you can go more wild with box perspectives like some weird angles or not a perfect cube but yeah you can do these with 250 box challenge.