Hmm, OP. Have to say, we might be more forthcoming with help if you can, perhaps, let us know exactly what kind of professor of which subject in a German university you seek. I'd recommend Google, but not in your case. It brings up 29, 200, 000 pages. If it, say, takes you a minute to check each page, then you'll spend nearly 6 years searching 24 hours everyday - including Christmas day. I don't know about you, but I'd be feeling pretty unmotivated about the idea of doing a PhD by the end of it.