These are all really good Windeh! You've got a knack for picking the right poses. If you wanted my opinion on what you should work on, I would say your proportions and maybe focus a bit more on anatomy.
Looking at your 3 newest drawings, in
this one, the left arm (his right) looks really uncomfortable/awkward. For one I think that arm is slightly too skinny at the elbow also his hand is facing in the wrong direction. I'm not sure if you understand what I mean about his hand, but his palms are facing away from the camera rather than towards it. Which is making it look like he is twisting his forearm. You added a long crease from his pointer finger on top of the outline for his thumb. If you just erased that crease which is making the viewer think his thumb is behind his hand, it would fix this issue. Sorry if this is confusing, I'm trying to explain it the best I can.
I don't have any complaints about the other two, they both look nice. I like the lighting you used in the background of your newest one. It looks like he is buried under ground and someone just dug him out and he/she is seeing the light of day for the first time in ages.
If you don't mind me asking, how do you create shading like that on the computer? You said you made your newest one on the computer. I'm guessing you use a tablet to draw the outlines, but how to do you make the shading patches? Like the lighting/shading in the background of your newest drawing.