Madrid is in our heart now. Big thanks is to Carlos for the smooth and helpful tips. Carlos&Frank helped me and my girlfriend as much as they can to provide easy and smooth stay, for example they provided us many options how to get to apartment and they we're so kind to organize us airport shuttle service upon arrival and on the departure.

So about the apartment: Apartment looked the same as in the pictures. It was pure and in good shape. Carlos show us everything in the apartment and helped us in our questions. He spoked really good english. I highly recommend the area of the apartment, it's easy to walk everywhere and explore Madrid. We didn't use puplic transportations during our stay because from the apartment everything we saw was in walkable distance.
Only negative thing was that when we booked the apartment and before our arrival we weren't told about construction works what was happening in our strairway. Carlos of course told us when we got there that what was going on and it was only in 1st floor (apartment was in 3rd floor). He said that they don't start too early their work, which was mostly right but one morning they started around 6 am. Construction work sounds mostly did the trick to get us up earlier than planned which was good but not they happiest alarm clock sound tough.
I would give this really good rate if they have only told us beforehand about the constructions...