Just a small combination of different elements, along with duplications and Boolean unions and differences. also tested out all the Sculpting operations.
I used Blender 2.8.
Congrats on your first rendition of a 3d model !
I really like the trees. The rest feels a little amorphous to my taste, but it actually does seem like a start of an interesting scene.
Why don't you go back to this render after you finish more courses and see what you can add ?
Thanks and all the best ,
Ido