The mountains are approx 500 meters from the camera, and they need to appear big and in composition they should acquire 50% of the scene(i.e. with the horizon which is the lake in this case). Firstly I based this off of actual distance range in real life because I couldn't come with other ways, so I put the mountains 500m from camera and made them approx. 100ft tall but then they consumed the sky. Then I had to shrink them down. But, as you can see now the problem with the scene is that, the mountains look like small hills that I fairly close by and the horizon a small puddle, whereas I'd like them to appear far from the camera and the horizon should look like a vast ocean.
How do I achieve this? I'll attach the .blend below with the textures packed.