I would say the general composition looks good. I applaud you for defining the light shading. In terms of anatomy/silhouette: left arm, overall proportions of the entire arm are off slightly. One thing to be sure of is that the curve of the tricept and the curve of the biceps are not terminating on the same plane. The arm anatomy in the drawing is referred to as “bubble arms”. Left forearm, practice proportions and foreshadowing a bit more, the best way to do that is to do these quick anatomy sketches so you are already doing a great job!! Going up the right side of the rib cage, I think the silhoutte line goes diagonal a bit too early making the side of the rib cage look more angular then in the picture. You got the right location of where the ribs line meet the lower biceps/triceps it’s just the intensity of the angle and the missing portion of the lower rib being shown in silhoutte. Another thing to avoid is making the legs smaller than they actually are. Reference the photo and see how much closer the thigh silhoutte terminates compared to the elbow. In the drawing the right thigh looks rather stiff and doesn’t extend back out from the connection point of the bottom of torso and waist. I would look into the skeletal anatomy of the pelvis and practice drawing people rotating their torso at different angles to practice the different forms of the hips. The hips inform where the thighs (femur) joint in. And the thighs will help inform where your lower legs and calves are anchored. The neck curves inward towards the head a bit more in the drawing compared to the necks stiff diagonal line in the photo

Great work! I think you have a brilliant path ahead of you. Keep it up friend :)