I'm not great at writing long paragraphs of general improvements you can do, so I'll just point out some likeness issues I see:
-His head is a lot more round, especially at the top.
-His edge goes a little bit further down in the middle, and up and pointier at the sides.
-Ears need to be larger and slightly pointier.
-His chin is a lot bigger, and pointier at the bottom, there is also more space between the mouth and the bottom of the chin, as well as more beard hair(visible).
-Maybe you'd want him to be looking right into the camera, as in the reference? The eyes in your version seem to be looking somewhere a little lower and to the right of him.
They also don't seem to belong to the same person, the eyes don't match as much as they should.
-Cheeks probably need to be more puffy, especially on the right side, it seems you have some lighting inconsistencies there.