I am showing here backfaces in pink:
Glass doesn’t render properly when doing single surface, and especially not when seen from the backface.
Select the surfaces you can see the backfaces from and use _Flip. After that it is a good idea to also select all the surfaces with your Glass materials and add the tiniest biit of thickness to them. 0.01 should do to keep them very thin - the glass will render correctly.
Below I just used the material editor to select all objects with the glass materials assigned, then in object properties panel I added thickness to 0.01
Select objects with specific material
Edit: The water you can improve still with a simple normal map. I’d disable the ground-plane, as you won’t be needing it. It just takes up unnecessary resources and causes unnecessary pressure on BVH building. Instead create a kind of a box around the bottom of your water body and assign it the same material as your hill. Drop the attached water material Wavy Water.rmtl (492.0 KB) on your water body.
Water body extruded down for depth, ‘earth’ box added around the bottom part
Render with wavy material and bottom of water body fixed