I think it's pretty good! You've missed the shadows on the right side of his lips though, which flattens the portrait and spoils the 3D effect somewhat.

Really nice contours and good contrast in the tones, Your eye for tones is better than mine.

Hey, @Bart Dirks, welcome! I know of basically two ways to prevent this: 1) Applying some fixative to your drawings after you finish them. You can probably find art fixative spray on your local art supply shop, since it's a pretty common item, or you could also try to purchase it online. Alternatively, here's a quick tip I got from an old teacher of mine: hair fixative also works just as well with graphite and charcoal, plus it smells better. 2) Sticking a blank sheet of paper (or a piece of it) on top of the drawing so that this sheet catches all the smudging and protects the opposite page in the sketchbook. When I do this, I like to use tracing paper or another type of translucent paper so I can see my drawings through it (I'm attaching an example image). Hope this helps!