Hi there,
I've just updated the asset pack, so sorry about that, yeah I forgot to add the mesh for the dock base (which is now included)
Also I'm not too experienced in Godot but from what I remember you have to enable transparency in the material settings to fix the tree issue. As for the textures being visible from only one side, be sure to set it to 2-sided textures (this will apply to the trees and foliage as well)