I'm a beginner as well (not sure I'm even a level 2 yet), so take this with a grain of salt. From what I see, I would say, be mindful of the angles and size relationship of the shapes. One thing I notice is that if I were to draw a line down the center, your drawing has the subject's head tilted to the left of the center, whereas the photo has him leaning to the right of that line. It's ever so subtle, but I feel it makes a difference. Then just be mindful of the size of things like the hair on the lower right, it looks really big. Hope that helps a bit. I will be posting my pears and two of this portrait today or tomorrow. Keep it up!

Nice job! I like the cleanliness of the measurements and attention to the perspective of the forms. As for some feedback, it's very smooth shading, but it seems soft to the point where the light source isn't as apparent at first glance. This may also be in part due to the strong reflective light that it looks like it could be a second light source. Remember that with reflective light, it still appears within the shadows and is part of the shadow group, so it will be darker than anything on the side hit with direct light. It helps with rendering to first block in the separation of light and darks, then add in the half tones, in order to have clarity between the two main groups. Lastly, remember that these are 3D objects, so don't forget the plane indicating their width. Since we are looking slightly downwards on the cups, we will see the top ridge that indicates the width of the walls of the cups, even if they are thin. If the light source is hitting from above, these planes will most likely be the lightest in value. Hope this helps :)