semi transparent texture with shadowing issues?

Hi,
I am brand new to Unity and have a simple scene with a bench and a umbrella, this umbrella has a slight over lap and when I apply the texture as a transparent/diffuse the overlap becomes dark as if its casting a show within it self?

How can I avoid this?

Also as I said I am brand new and cant seem to find a good entry level tutorial for creating custom shaders? I cant even find out how to get into the code?
any suggestions?

Thanx! :slight_smile:

[9473-ref+image.jpg|9473]

I ended up fixing the model in 3ds max so that there was no longer an overlap and it now renders fine.