First, thanks a lot for the compliment!π
I think it's a kind of routine to get the hang of buliding hills, mountains, rivers etc. I like to use the premade settings from the scenarios to inspire me and build from that.
As you can see, the hill/mountain by the wooden-coaster is completely build by me. But for example I did it, after I made the coaster.
And as far as a forest goes: make two or three hills, take two or three tree species, place them around an area and add a few ground textures to that, and it looks instantly nicer!
Never stop tryingπͺ