Finally made it :)
I used a hacky Way.
I am using 3D shadows and a second camera.
The second only films the layer with the 3D objects(shadow & light) and renders that renders onto a render texture.
I use a shader to combine blend these images together.
Shader: https://github.com/prime31/SpriteLigh...
Image of the SceneSetup: https://noobygames.de/wp-content/uplo...