Well, it is a difficult one, please read it through. In two words, it was the worst experice one could experience after a tiresome day. The photos of the hotel advertised on their AirBnB page are incorrect. Instead of a light, clean, gorgeous room with large windows, a double bed, I was given a 3m2 dark room on the top floor, smelling cigarettes and the bathroom, which I rather call just a shower "cabin" was so small I could hardly enter it. (Room 607)
When I went down to tell the problem to the concierge on duty, it is not that he was not courtois and kind but became agressive, which did not help. He said I got what I reserved. I spent a horrible evening there as it was too late to look for another hotel and contacted AirBnB for a refund.
However, I do have to mention, that the following morning, as I was leaving the hotel, there was a wonderful person, a woman, who apparently was one of the managers, who was aware of the problem and tried (very kindly) to help.
If the handeling of the problem the night before would have been different, the room would have been still the same but without the bitterness and agrevation. My advice is, if you ever want to stay at this hotel, call them before and make sure to get what you are about to pay for. As a result, I had to shorten my trip in Paris, which was highly regretable.