Thank you for your answer,
1) "Airbnb will notify you about it and the reservation can/will be ended mean in concrete terms?"
What does it mean in concrete terms ? What happens if the traveler don't agree with the ending ?
2) From a legal point of view, having 2 contracts that add up is not a good idea. What is the use of using Airbnb if you have to make your traveler sign a rental contract? Most people interested in long-term rentals ask you to sign a contract outside Airbnb. When you report the problem to Airbnb, they tell you that the problem is known, but that it doesn't matter because Airbnb offers guarantees that you wouldn't have with a rental contract.... What special guarantees superior to those offered by a rental contract offer Airbnb?