The coloured ones are looking good ^^
As for anatomy; firstly, don't be afraid to make a neck as wide as the head; necks are actually that big. look in the mirror if you don't believe me. Be careful with this, as there is the visual illusion of the necks appearing smaller. So be subtle about it too. It comes with practice.
The method i use to build anatomy uses head sizes. This is just something i memorized a few years back and recall it every time i draw a person, though it's worth constantly building on it and noticing things about the sizes and shapes of peoples bodies for yourself; drawing from life is 100% worth every second and you'll learn it much faster this way. If you don't have real life models and can't find a mirror, i like to use
https://www.posemaniacs.com/
A good practice is using the 30 second poser and drawing each pose within the time limit. very difficult at first, but you soon get used to it and you'll notice the improvement within a few short tries.
So thats the practice and perseverance side of understanding anatomy, heres the technical side; the proportions.
Everyone is different, and every time you draw someone it'll never be the same twice, so you can pick a constant. The easiest is the head, since that were you, like many other people, have started drawing from.
There are two general formulae for creating the human form in this way:
Males:
Neck is half a head size. Shoulders vary from two head sizes across to one and a half for the less-heroic types. Bellybutton is two head sizes down from the chin, level with the tops of the hip bones. Hips are about 1 headsize across. Forearms are just over one headsize, while the upper arm is just under one headsize. Hands are the size of the side of the face (check on your own if you don't believe me)
Legs can generally be stylised but a safe bet is two headsizes takes you down to the base of the platella (kneecap) and then another two to the heel. A foot is the same length as a forearm (again, check for yourself)
Females are the same as males besides the general smoother shapes on all parts (plus the obvious additions, i.e boobs, the top of which will be in line with the armpits give or take.) due to a higher percentage of bodyfat. Shoulders should be about one headsize wide, the waist should remain the same for a male however the hips should widen to two headsizes across.
With practice it'll become easier and you'll notice what makes the body work and look natural. Try to work with curves while mapping out the skeleton to make the figures look less stiff.
I think thats plenty for you to think about for next time.
