What is writen here?

[rexmundi]

Anyone an idea?

[Tim DC]

I'd say Fliegert b. Meijel, though I'm not 100% sure on the first word.
Fliegert is a German last name, so that would make sense.

[Gerdan]

In the middle in the background there is written an other German family name: Voigt.

Gerdan

[Tim DC]

Yes, that's probably the name of the previous owner of the photo, while there is someone else shown in the photo.