Welcome ! :) A few things : - The head looks too big. - The biceps/deltoids/triceps area is too blended together, try to define each muscles separately. - Don't forget the tip of the claviculas where the neck muscles attach, it's a visually interesting area. - The forearms look too thin, it looks weird especially from side…
His shoulders and the muscles around his upper back, especially the Teres Minor/Major look too large and blobby. It should suggest that they are lying gracefully under the deltoid. Some more reference on the back muscles as it seems you pay too much attention to defining muscles such as his pecs and buttocks too early. I…