In the story, you’ll find
«διαμέρισμα μου»
This should be
«διαμέρισμά μου» because of the possessive pronoun.
Additionally,
«το διαμέρισμα του» (when not followed by Βασίλη)
should be
«το διαμέρισμά του»
For example, the following two sentences occur consecutively. In the first, there should be no second accent mark, as it’s “Vasili’s apartment”. In the second sentence there should be a second accent mark because it’s “his apartment”
«Είναι το διαμέρισμα του Βασίλη μεγάλο;
Όχι, το διαμέρισμά του δεν είναι μεγάλο.»
(Well the text has “?” for a Greek question mark, which is accepted and understood, but not grammatically accurate.)