Focus looks fine judging by the rails beneath him/her. Shutter speed could have been a stop or two faster to freeze the skater in midair, or a stop or two slower for meaningful. motion blur.

Composition is OK but I'd try to get closer if you can. This looks like a 50mm field of view? You didn't say what lens. An 85 or 105 might be another lens to consider for skate park work, just to get closer without getting in the way of the skateboarders.

Another good lens in this range is a Pentax/Kiron/Promaster 75-150 f/4, a decent and cheap zoom lens. It's the same lens as the well-regarded Nikon Series E 75-150 f/3.5, all of which were manufactured by Kiron and are actually a f/3.8 aperture, although depending on who sold them it may have been marketed as f/3.5 or f/4. You can pick up the Pentax K mount version for $40-50.