It's impossible to say why you're getting the error you mention without more information. For anyone to give you any advice outside of educated guesses you'd need to provide us with the details of how you have replication configured. So for now I'll give you an idea where to begin.
- Look at your schema on your subscriber, LORENZ, to verify that a foreign key exists.
- If the foreign key exists then something you did put it there. My guess is that it was copied to your subscriber during the snapshot, I'm pretty sure of this guess by the way, like 99% sure.
- If it turns out you have a foreign key on your subscriber then you need to review your snapshot configuration, it's likely you inadvertently set your snapshot to copy the foreign keys to your subscriber.
If my guess was right and your foreign keys are being copied to your subscriber during the snapshot process then the fix is fairly easy. There's a replication stored procedure called sp_addarticle which takes a parameter called @schema_option. The parameter @schema_option is a bitmask which allows you to tell the snapshot agent whether or not to copy foreign keys among other things. You can see the official documentation at the following URL.
https://msdn.microsoft.com/en-us/library/ms173857.aspx
Specifically the bit at 0x200 controls replication of foreign key constraints.