I have stayed in this hotel for several years now for an annual event, and my experience with its staff has been on a steady decline. They are rude, they lie blatantly to your face and have no concept of customer service whatsoever.
The hotel itself is okayish, definitely not a 4 star hotel though. The amenties in the room are quite basic and cleanliness is ok.
My room had the rain shower head not working, so only the hand shower not worked and it had a low mount which made it inconvenient to use. The breakfast is ok, but for a 4 Star hotel, it's lacking and chaotic when it's busy. The only thing that this hotel has going for it, is that its very central location in the heart of Alexanderplatz, but honestly there are plenty of other better hotels around the square. I regretted booking this hotel.