For a first track it's a really great effort, although I'd propose a few things for your future tracks:
- Try to shape the layout in some other way than just 90 degree turns, because these corners all feel the same. It's a lot more fun to race a diverse track.
- Tracks usually aren't built in the middle of nowhere with no access roads. Try to "connect" the track with civilisation.
- Forest all around is most of the time just a way of saying "I've no idea what else to put there". Try to use your imagination and make use of the different objects that are available. Elevation changes and lmap dithering can be great monotony breakers too.
- Also about forests: make some random gaps and clusters of trees, some paths, areas with bushes and maybe some stones to make them more beautiful and realistic. Trees don't grow in perfect patterns in nature, why should they in GR?
- Leave some space in the pits for cars to drive past the pit crews. You don't want to be responsible for injuries of those nice guys, do you?
Also try to include more (all) pitcrews, if you have space like here.
Those are just some general pointers you should pay attention to next time. It's a solid first track but of course there's still room for improvement.