it is kind of tricky when it does not have certain angle, when you are looking strait at it, that means that you can`t see bottom or top of the object. On this pic, I would say that parts that you pointed out have a super small angle, almost looks flat, so you did it almost right. I am not sure how far you got with art school, but Marc explains it really good in video Nude figure drawing (term 1) at 36:15 min just keep practicing, the more you do, the more you will understand, you are on a good way