Flat is ok for max.2 people as it is small and the ceiling was too low that average tall person has to lower his head to walk through some parts of the flat. Also I would not recommend this place if you stay with a child because for going to kitchen/toilet/bath you need to pass the stairs without any railing.
Sound isolation is so weak that if upper flat is occupant even if they are careful you would hear all of their conversations and steps like they are in the same flat. There is a small window in the bedroom but keep in mind that if you open it there are pipes coming from nearby restaurants kitchens’ ventilation and all the food smell is in your room right away.
Otherwise if you are two people staying for few nights flat is more or less ok. Location makes it better so you can skip paying attention to some disadvantages inside.