Hi.
About buildings : Looking at your sketches, I think you managed to draw something that feels much more grounded and realistic on page 16, simply because you took the time to set proper construction lines using 2 vanishing points. Keep using those for your buildings, and with practice you'll manage to be much more accurate by simply eyeballing references.
About objects : Some objects like gun, trumpets, or swords feel way off, but I think that is because you're immediately trying to get the details you see. Try constructing bigger shapes first and connecting them with details later. At your level, i think you should practice perspective on simpler objects and practice complicated objets in neutral pov. Once you feel comfortable enough, try foreshortening guns and whatnot again.
About figures : You like boxes, it has it's pros and cons. Boxes allow you to better set the orientation of a body part, but at a cost, your figures feel very stiff. I'd suggest starting with a line of action (TM). It will dictate the flow of your figure. Try using ovals for torsos and hips, and use them very fluidly when connecting them. For more dynamic poses, don't forget about "contrapposto" !
Good luck, and keep the good work :)
