Certain Parts of Terrain Too Dark
Certain Parts of my terrain seem quite dark.I dont know why. As you can see in the image the left part is dark and the right is normal. It feels like shadow or some lighting problem.
Screenshot :
It's dark because you're using a single, directional light that's being a blocked by the wall on the left. Have a look at the Lighting window for your Scene: Unity Manual for Lighting Window
There, you can play with settings like the "environment lighting" and its source. By adjusting this, you should be able to add a base amount of illumination throughout the scene.
If that doesn't work, you'll need to add more lighting objects to your scene. You can try to balance more directional lights from other directions. Or you can add local lights like spot/area lights to illuminate surfaces left in shadow by your directional light.