Looking for a niche provider - not one of the usual suspects like Colt or GTT or Deutsche Telekom. A carrier with a dense German network hitting the smaller cities like Nürnberg. Wholesale mentality. Gige, 10 and 100 gig waves. DF.
The big guys don’t cut it.
Depending on your specific needs the first I would think about are EUnetworks and Gasline.
For Nuremberg specifically I suggest to ask Core Backbone and Noris.
From what I heard Gasline sold their Layer2 operations to EnBW if I recall correctly. I think Gasline has only DF left.
Re Eunetworks: I recommend to avoid them, unless you don‘t mind be taken to court for their own mistakes. No joke.
To get better answers or more regional suggestions try asking in the DENOG mailinglist.