I can do hard surface modelling pretty well but I dont even know where to start for trees and rocks… I can’t get the shape down right
Organic modelling is so easy with polygons! It’s why polygons exist! Are you sure you can do hard surfaces with polygons?
Do you have two monitors? Put a picture of what you want to model on one monitor, and model it on the other. Simple!
The hard bit is UV mapping organic models for textures.