I didn't get a chance to meet Dennis during my stay. It seems he doesn't live in the apartment. Check in was really easy because there is a numlock on the door, however the day I arrived it was quite a surprise because the apartment looked nothing like in the pictures. Kitchen was covered with dust and in the living room there were just chairs and rolled carpet on the floor. From first impression I'd say that no one lived in the apartment for a while.
However, my room was nice and clean. Next day Dennis mom came to clean the house so basically she cleaned all the dirt and then it was OK.
The neighbourhood is 15 min walk from National Mall which is amazing but is a little bit eccentric and for my late arrivals I always took an Uber.

Overall, the experience was different to what I expected according to pictures and reviews. But Dennis was really helpful and responded to all my questions before my arrival.