We really enjoyed our stay! The communication with Carlos was really uncomplicated and very friendly. The flat is exactly like in the description, also very clean. It can be a bit noisy at night because of the bar underneath but that wasn't a problem for us. The flat is very central. A lot of restaurants and bars are close and it takes a 10-15 minute walk to the Douro, to the metro (way to the Airport) it's only 5 minutes and to the rail station São Bento it's a 10 minute walk (way to the beach).
Carlos was a perfect host, thanks!