I was not previously aware that such a problem existed at this level. Upon learning of this situation, I put all conceivable efforts into solving the issue: I contacted the building administrator. I was able to obtain another comprehensive extermination procedure throughout the building. I deeply cleaned the apartment for the next three weeks free of charge. Also, as soon the issue arose, I offered to refund the entire amount paid if the renter chose to go elsewhere. Instead, he chose to stay. In the end, as a matter of correctness, after the renter had stayed for the first month, I refunded half of the money agreed upon, using the airbnb customer service, with which I was also in contact. In the end, after the renter departed, I was disappointed to find the apartment had been rather neglected during his stay, and once again, I had the clean the entire place.