Alex's apartment is perfect to spend some days in Berlin. The location was great, 10 min walking from the station Hauptbahnhof, where there are lots of trains, metro, buses... The neighbourhood is very nice and quiet and so is the apartment.
The place is clean and as it appears in the pictures. The communication with Alex was perfect, he explained us everything before our arrival.
I totally recommend his apartment for your staying in Berlin, an amazing city, by the way :)