First time I have a bad experience with airbnb. The host (a rental agency) is not professional at all. We faced many issues during and after our stay but they are hardly reachable. We felt like the agency is not really considering our complaint. For an agency which claimed to be a "conciergerie", the service is extremely poor. I certainly not recommend them.
Regarding the apartment, it is nice, very clean and well located, you can go everywhere by walking. The area is very noisy with bars and restaurants downstairs. It is close to the sea, therefore the seagulls are screaming all night. They probably have a nest on the roof of the building, so bring earplugs to sleep at night. There is no living room, only a small kitchen. However there is a nice balcony around the apartment, perfect for breakfast!
It was not specified in the ad that the biggest bedroom has no door, which means no privacy at all.
Anyway we had a pleasant stay in Porto where the inhabitants are super welcoming and lovely. :)