Hey there :3

Firstly, terrain. You have a nice amount of terrain, with good diversity and layers. There are some flat areas you could raise (the areas between the water. I really like the palette though, good choice of blocks!

Secondly, organics. Some of your trees are a little too thin in the middle, and a couple are too thick. The roots are also too /flat/, and not spread out as much as they could be. A couple trees also don't have roots at all! Make sure you add them.
The leaves, remember you have world edit, so you can use a brush for the leaves! Just make sure you have a high air percentage in the brush.

Lastly, structure. I love the helicopter a lot! I also like the structures, but some of the detailing can be changed on some of them. The tower, you should add more of a curve to the stonebrick supports, so they don't go diagonal. I'd also suggest not using mossy cobble walls for detailing the entire wall!

Good luck!
- Dutty :3