How can i apply a PNG logo on my material? I have a project with a material I want to add to my sphere. I want to add this logo onto the sphere. I have tried various ways of uv mapping but I keep messing up :/ 

This is my current material setup:



And here is what I would like to have: 



EDIT:

I have now changed my setup like the answer stated, but my material still changes with the PNG, so it becomes black although my material is red

MY SETUP (NEW):

Something (probably a small setting) is stil wrong, but I can't figure it out.
you need a "Transparent BSDF node (see image). PM if you get stuck