Frank's flat is as described, cosy and well located. The bed is comfortable, there is space for one or two people to live, everything was clean.
The neighbourhood is nice, full of small shops and parks (big plus: many restaurants with vegetarian and vegan options!). The flat is just a few steps from the metro, so you're within 25 minutes of everything you'd like to see during your stay.
Small downsides: communication was complicated on arrival, Frank didn't answer my messages and I had to call him once I arrived at the apartment to get the code to enter.
Other drawback: no ventilation so annoying to cook, otherwise you have to open the window which looks onto the street. And sometimes a cold in the evening.
Despite this, I would definitely recommend it and would be happy to come back!