Hello :)
first of a it´s a really good game!

SPOILER:
In apartment 113 you need a password for the terminal.
There are pretty cool hints. In the german version I solved the puzzle, but the password was not accepted.
You can find the Password in the green Book

In the German version the book reeds: "Gertrud, die Schwester der Weisheit".
But the password gertrud didn´t work.

In the english version the book reeds: "Melinda, sister of prudence"
The Password Melind worked in the german version, but there is no hint.

An update by changing the name in the book into Melinda would fix this :D

Ciao
Ben