Communication with Isabel was perfect. José was waiting at the appartment and very kindly offered Porto. :) The apartment is very clean with nice design. Some light switches are not working but it's a minor remark. It is very well situated (2 minutes walk close to metro/bus station and walking distance from the heart of Porto, bakery and various shops nearby,...).
My only concern is not directly related to the apartment: being on the first floor the traffic on the street can be a bit disturbing (e.g. the public street cleaning service can be heard around midnight/1am every night, also buses,...).
I warmly recommend this place.