my best advice is to get confident in your linework. the proportions look good! the positioning makes sense! the only thing i really see is "sketchy" linework, which does not look as polished when compared to smoother, longer lines. you just have to make what exists look "smoother"

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Make the transition from wrist to forearm longer, it goes up in size too quick. Another is enlarged the hands as make the arms larger overall as the bicep is smaller than the forearm. Lengthen the Aron on the right side atleast in the elbow to hand area. This is due to it being shorter than the elbow to shoulder when in reality when you bend your arm your elbow to wrist is approximately the same length as shoulder to elbow a whole hand adds several inches to it (or one hand length longer)

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