This apartment is enormous! I stayed in Martha's apartment with my family, we were five adults, and we were extremely comfortable. There are two bedrooms with double beds each, a single sofa bed, and two other sofa beds in the living area. We absolutely loved how bright the flat is and really appreciated how well equipped the kitchen is.
The location is great as well, you can walk to all major sites and a train station is a few blocks away. If you can, make sure to be there on a weekend to enjoy the market in full glory!
Please note that this apartment is on a third/fourth floor and it doesn't have an elevator - my parents struggled a little bit with the hike every day.
Overall I am very happy to have stayed in this apartment, Martha and her daughter will certainly make you feel at home. Thank you both for your warm welcome!