Objects shadows are overlapping each other

[Command: Manick]

I've just recently started trying to learn on my own how to make my 3D projects look more realistic, and after some of my own research I've finally found out how to enable ground shadows, but I'm having trouble figuring out how to make it look right. All of the 3d objects on my drawing are enabled to cast and receive shadows, and I am aware that I can change some of them to only receive shadows to eliminate some of the problem I am having here, but not entirely. Is there an easy solution for this?

 

Also, I have a couple more related questions.

 

For some reason I can only change my visual style properties to either display ground shadows, or to have objects receive shadows, but not both, which doesn't seem right. How can I get my objects to cast shadows on one another AND cast shadows to the ground?

 

And my last question has to do with object shading. I am using a sun & sky to control the shadows, if that is of any relevance. How do I make it so that whichever side of my objects is opposite of the suns light, not show up to dark? It almost is completely pitch black, and I can barely even see the materials at all.