We simply cannot recommend this apartment after a terrible experience. After 3 attempts at contact a few days before our stay, Sandra eventually responded to my messages and told us we could access the apartment at our late arrival time by retrieving a key from the lock box by the door. When we got there and opened it there was no key, it was midnight, and Sandra would not respond to our messages or phone call. We had to search the streets for an affordable hotel that we eventually settled into at 1:30am (Use the Arcotel Wimburger if you are in the same unfortunate situation - they were very welcoming and supportive).
Sandra did obviously realise her errors in the early hours of the morning and met us at the apartment - in her words, to apologise deeply. However, all we really got was a 'sorry I forgot and had personal problems yesterday'. She made no attempt to even contact us throughout the rest of the stay - perhaps wanting to avoid any further embarrassment. She did refund us for some of the stay (only after I asked through Airbnb), but not what we had paid, but to be honest, we just wanted to move on.
What a shame as the apartment was pretty nice (though the bathroom door was falling off until we fixed it - though it is missing screws to safely secure it, we were left one and a half toilet rolls for a 5 night stay, the dishwasher was not working and the pillows were rather too soft). Our feelings were certainly coloured by the whole experience but the area was amazing (near to Spittelburg Xmas market and great nearby restaurants and cafes - try Westpol, Marks and Erich's - all delicious). We would return to the location but find somewhere to stay.