The location of the flat is great. We could reach everything by walk. The flat also looks really nice in its overall design. The only thing that felt a bit off were the basics. As others have mentioned, one could feel that there is no one really living (like the scissors didn't cut well, or the pan was slightly small, so you couldn't comfortably cook for two people). We were also unlucky as there was a construction site in the street, so you had noise from outside for most of the time. But that seems to be a thing in many parts of Porto, so I guess that's not really an argument against this flat in specific.
All in all it was a good stay and I'm sure that the hosting agency will improve those little details in the future.