It basically explains how almost every department in Mexico City working with AirBnb belongs to one person, creating a hellscape for any person trying to really live in there (if u want to become even more depressed; https://politica.expansion.mx/cdmx/2022/11/04/mr-w-airbnb-cdmx-incrementa-1600-renta-departamento-condesa).
We need to try staying at local guest houses/hostals maybe even hotel's, to not make things worse.
And I really love the concept of Gasthaus, I envy u Germans !
Gasthof is what OP is looking for.