Congrats on your first attempt :) I like your clear value distinctions and portrait likeness for this piece. Something that could help is thinking about where the light source is coming from and how it affects the subject, i.e. how the light rays land on his face. Because it's coming from the right and a bit in front in this example, it'd help to check for and reinforce the light side as being on the front and right side of his face, while the left side is mostly in shadow, including the neck. Smaller plane changes that could block light are also good places to check, like under his brows, nose, and jaw. Another tip for painting is to keep a variety of hard edges and soft edges to make it feel more natural and balanced. Especially when there's a sharp turn, the edge will appear much harsher, while a more gradual transition, like a curved surface, will have a softer edge. Hope this helps and let me know if you have any questions. Happy painting!

great job! you kept your lines simple.

Detail level is too much. I think maybe you rushed it just a bit? Also try using a smaller brush.