As soon as we entered in the apartment, we noticed a musty smell. Then we saw plenty of stains on the walls, as well as on the sofa. Let's say that the apartment was not clean at all. But since we had to spend one month there and it was fairly central and spacious enough for two people, we thought we would clean it and try to make it comfortable.
Unfortunately the same night we saw a cockroach and the morning after we saw more. We decided to spray insecticide through all the holes. We sadly found out that it was a real infestation with dozens and dozens of them coming out from under the kitchen. We contacted the host and he only asked for proves. Once we sent him pictures and videos, the only solution he provided was sending a cleaning lady with insecticide. Which was very useless given the fact that it was a cockroach infestation. By the way, she told us that "these things happen especially if people or guests leave food". Very empty words. That was a huge cockroach situation likely to be already known from the host.
At that point, the host (actually some GuestReady worker) told us that if we wanted a refund we had to talk directly with airbnb. And that's what we did. We talked with them, sent them the same pictures, and they directly cancelled our booking.
Cherry on the cake, GuestReady called at 9pm of the second night to remind us that since our booking had been cancelled, we had to leave the apartment immediately. We were happy and ready to leave it, but yeah, this is a conclusive evidence of their bad service. Two days after I had the full refund in my bank account. This is the only positive note of our horrible experience with this company.