Help for topdown 3d game terrrains

Hi,
I a unity self learner trying to build first mini game struggling with the quality of the terrains , illuminiation and modeling, i m in the basis a coder, but learning
Besides that can you hekp me understand why cant i get goodlooking terrain for my top down project.


i hav, grass , sand , and basic layer for generic terrain texture for my byclicle game

This is not for a commercial product but when i do things i like them to have a litle bit of quality

 

That's art direction and game design, having things look good require a lots of trial and errors, but I think this is a pretty good start, except that I don't get what are the grey zones, there should be a texture under the grass too. Plus you could add some lighting. Please notice also that this is an editor view, not the player using the Unity scene camera. So you can't have any effects or camera settings, this is the 3D view.
Generating or creating realistic or good-looking terrains requires a ton of work, years of experience, but you can save time using third parties terrain assets, like gaia, world composer or terrain composer which are all great in my opinion.