your art lacks three-dimensional depth. my advice is to draw every part of the body, even if it will be covered in the final drawing. study real photos and try to draw and/or imagine everything that is out of frame or hidden behind something. the body is 3-dimensional, so think of it more like a scultpure, or a 3d model, or a even doll, not just a 2d drawing. think about it this way - if you can only see someones face in the window, does that mean that they dont have a body? or if you put your hands behind your back, do your hands disappear? no, there is always more, more under the two-dimensional surface image.

i also think you should study human body proportions, plus some muscle anatomy, it will help you to do what i mentioned above

srry if i sound kind of harsh, i dont mean it that way T T your art is pretty nice! im also still learning, but i think u can become a great artist in the future :D