I was staying at this apartment with 2 friends of mine for two nights. We thought that the location was perfect since there are good public transport connections to all the main sights in the city. A bit surprising were the many stairs leading up to the apartment which in our opinion was not clear from the description. It is definitely not advisable if you have big suitcases since there are 7 flights of stairs (4 floors). It was very nice of the hosts that we were able to already enter the apartment at around noon for an extra fee of 5€ for a key deposit box however you noticed that they only had 30 min for cleaning. For example there was a used towel of a previous guest still hanging in one of the rooms and the whole apartment smelled a lot like cleaning supplies. In general the apartment could have been cleaner - the fridge is anything but clean and neither are the cutleries and the drawers. Cooking there was therefore not an option for us. The apartment is nice, light and quiet however if you are three people the living room is transformed into a bed room which doesn't leave any room for a cozy time hanging out other than the kitchen table (which is however very nice!!). Since the apartment is also a lot smaller and less open than it looks on the pictures we thought that the price was a bit high for what the apartment offers. We were disappointed to not have met the hosts at any point. We picked up the key from a key box and left the extra money and key in the apartment at the end. We were missing the personal touch and the charm since it felt very professionally run by the owners - we could have gotten the same staying at a hotel which was not what we were looking for.
To sum up it is a cute apartment for a short stay in Berlin but pricey for what it is.