Looking really good Fizzy! Think you are getting a good idea of these objects in space. The only real issue I see is the cylinders don't always appear to be at the correct angle, or are rectangles. For example I would suggest drawing an elipse through the cylinders at least 5 elipses at each end, middle and each quarter, something like this will give you a much better understanding of the form of the cylinder. Here is an example of one I did recently.
I would do the chest and pelvis boxes just like you have done on yours, but really focus on those elipses on the cylinders, its a super important skill that will keep coming back! It will be super hard at first, thats normal. Just keep at it! Hopefully that is helpful Really nice job so far keep it up and let me know if you have any questions.