The flat is exactly as described in the listing.
It is super clean and cozy. It totally works for one person.
There are no windows opening up to the outside, only to the stairway which might cause an issue at night when people go up and down the stairs and the lights come through the little windows in the room. This wasn't a massive issue for me as it's been overall quiet and luckily I had packed a night mask. The WiFi signal is not bad: I used it to do a couple of work calls: no issues. Shower gel/hand soap bottles were practically empty when I arrived: had to buy mine on the first day. The washing machine on the 2nd floor is available for you to use and a great addition! Overall, I would highly recommend it for a short stay in Porto.