not bad for a first try.
you just need to experiment with the terrain tools and learn to smooth and optimize.
also, when you do your planting, vary the types of trees alot more, and maybe throw some bushes in here and there. all your trees are the same height, you can vary that by entering a number in the +/- field.
when making sand bunkers, try using the create bunker tool, and you can draw 2 shapes, one outside the other and use the tool to make the slope or bunker between them.
the tuturials at smilioats.com can teach ya alot of that stuff, they helped me.
other than those things, you are on the right track.
keep it up