The connection to the existing Fritz box 7390 was with the instructions very easily and was also within a minute. The second Powerline adapter we then put into the basement apartment in an electrical outlet and - once the LAN connection was established via the power grid with a transmission rate of 150 MBit.
The apartments have their own electricity meter. That is, the LAN goes over the power cord into the cellar on the counter of the first apartment out in the second counter pure and from there to the outlets of the other apartment.
Conclusion: very easy to install, very good in performance