Hi,

your boxes aren't bad, and you shouldn't worry about them being wobbly at this moment - this will improve with practice and you should be realy patient with this. It seems that you understand how to construct box but you only need practice and practice (as we all).

Here are some advices I learnt from others and/or found myself:

First thing you should take care is line quality, draw lines with shoulders using ghosting and not too slowly but not too fast, you find speed appropriate for you with some experimenting. Also don't press pen too hard to page - keep it in relaxed hand - and this improve your line, save your wrist and pen.

Do ghosting and drawing lines with your writing hand touching lightly a paper (probably an english word for this is hover but I'm not sure).

I think you draw maybe too slow and too carefully -but maybe it just looks this way on photos and I'm wrong.

Do hatching also with ghosting and drawing with shoulder.

Hope this will help you, good luck

Greg