Frank's apartment was at a central location near Alexanderplatz and convenient for walking over to several attractions within the city. He also offered some good advice on where to visit and his personal opinions as well.
We had asked for a check-out a couple of hours after the stated time and Frank obliged.
The apartment itself was a cozy studio which had a bed, a couple of chairs and a small bathroom. Couple of inconveniences we faced: one, the toilet commode had a strange design and the flush took some time. Also, the other major one was the lack of a fan/AC in the apartment. Since it was quite hot in Berlin, we suffered due to the lack of one even after keeping the windows open. What would've helped is if Frank responded promptly to our email (we didn't get a response at all) to help address the situation. He later explained that he couldn't purchase one since it was a Sunday.
Overall, would recommend the place due to the location/price but hope my experience helps set expectations for other guests looking to book this apartment.