Thanks ...
@Kadri: This 'diffuse' lighting makes it very difficult to spot the shadows. For me the grass do not look like floating, but this due to my subjective impression (as I know it sits on the ground)

Nonetheless it is a good advice for an objective improvement by reducing the softness of the shadows.
About the lighting:
- Place your camera.
- Turn off the sun
- Add a lightsource and put it somewhere
quite close to your scene. In the image the camera is about 8m from the Bot, the light has an approx. distance of 16m - Increase the strength of the light to something that makes the scene be lit up ... I kept about one third of the scene quite dark. Play with the exposure!
- If the falloff of the light is too strong, move the light closer to your scene and/or change the Max distance of the light for finetuning
- Turn on Soft shadows ... these will only show up if the light source has a diameter larger than 0. The higher the diameter of the light, the softer the shadows and the closer the light, the softer the shadows. The quality of the shadows depends very much on the render quality ... make a crop of a shadow at quality 1 ... if there is still noise visible, you can increase the Soft shadow sample.
- Then we have fog ... I placed the standard Cumulus at a height of 0 and drew down the density to my needs - the fog lightens up the scene and I wanted to keep some strong contrasts - the fog gives this touch of diffuse lighting.
- Last, not least the EnviroLight: strength on surfaces got increased to something about 2.
- The objects colours are a bit insane ... the yellowish stuff for example has a light yellow colour and I changed the numerical value next to it to 4 .... this may cause the atmosphere to glow in fancy colours ... thatswhy decrease the envrolight strength of the atmosphere
I hope, I was able to help