I know RadioNEET was already aware of this but just to re-iterate, the perspective lines are all over the place here. The dots represent the horizon points from various lines on the drawing, and they should all line up to a horizon for 2 point perspective. Unfortunately, I know that RadioNEET drew the BG freehand and also AFTER drawing the girl which is a common faux pas.
When drawing a picture with a background, ALWAYS draw the background structure and perspective lines first! Otherwise it will get confusing trying to fit the BG to match the perspective of the character as is the case here. Then if perspective is not your strong suit, you can draw a perspective box/envelope around where the character should be to reinforce it.
Again, here I’ve put in the horizon in purple with 2 point perspective which shows (based on the table’s perspective which is the focus object) what the lines would actually look like. The warping becomes pretty crazy, because the horizon points are very close. The girl’s perspective horizon points are actually very very far, that’s why she looks flatter than the BG. The BG should have been drawn with the girl’s perspective.
When drawing stylized stuff (like anime style) people tend to draw objects very thin. It’s a common occurence. For example the top of the chair was almost 2D, with a very thin arch. Always mind the thickness of objects, this also applies to clothing folds. If you focus too much into one thing and not looking at the overall picture, you will get this effect.
Also the hands here are too small. The hands should always be comparable to the size of the face. By rule of thumb, it should cover your face until the eyebrows. But for drawing super deformed things (like chibi) the rule is relaxed. Again, objects on the body are too thin to be natural. In this case the forearm and leg calfs, apply volume to these muscles otherwise it looks like they are atrophied (like a bulemic/anorexic).
The arrow on the foot indicates the direction that the foot should be pointing. I know that because of the perspective warping that the foot looks contorted, but the rest of the body doesn’t follow this.
Another point is the positioning of the knees! If you do this pose yourself, you will find that the knee of the leg in flexion (medical term for bent) should be lower. Small details like this improve the realistic qualities of a drawing.
Nothing much to say here since the pose is generic. The neck could be considered slightly too long but that can be attributed to style (like Raita). The only problem here is the rendering of the cuff title on her right arm. It is too flat and vertical for that arm position. It needs to be rendered as if it were on a cylindrical surface pointing towards the viewer. The breasts are also slightly high.
Again, the problem here is the rendering of curved surfaces, namely the arms and the vest straps. They need to show more curvature, otherwise the arms look kinda flat.
A minor detail, for that right hand position the AK74 would deviate slightly on an angle because the centre of gravity (the green dot) needs to be balanced between the two fixture points, namely the hand and the blue strap. For static (not moving) objects supported by multiple pivot-like fixtures (as in not rock hard but floppy), the moment (or torque) around the Centre of Gravity (CoG) of the hanging object should be zero. That is to say, the line horizontal and perpendicular to the gravity vector (the arrow pointing down) must be equal on either side (i.e. the horizontal lines between the CoG and the green arrows pointing up).