@Serhat7
You said ...."But they damaged some little things and behave like nothing happened."
Serhat, we are finding it hard enough to get any form of compensation through Airbnb from a guest who will not admit to damage when the stay runs it's normal planned length and everything works within the platform.
To even consider lodging a claim when your 'friend' has worked outside the Airbnb charging structure with a guest is a surefire way to have the property and possibly the account closed by Airbnb.
You have to weigh up the consequences.....
On the negative side.
1/..........The guest is going to give a bad review....no guest likes to be challenged for more money and they will retaliate!
2/......The guest only has to say to Airbnb that they have paid the host additional money that did not go through Airbnb and should not have to pay any more, and Airbnb will take action against the host.
3/.....The chance of compensation is small, it would be an adjudicated amount and certainly not what would the host would be asking for. Airbnb will consider things like 'wear and tear' when offering any sort of payment.
This sort of action would only be considered if a large amount of money was involved.
Coming back that first point Serhat, if the damage was minimal, the host should just replace it out of their own pocket, do no more than say to the guest how disappointing it was to have to replace breakages, but it has been done, in the past now. This will embarrass the guest and they will probably still give a good review out of a feeling of guilt.
Serhat, there are battles you fight and battles you don't. I think this is one battle that the host should walk away from....by pursuing it they may very well be much worse off!
Cheers......Rob