Posso chiedere agli ospiti di firmare un contratto?

If you require guests to sign a contract, you must disclose the actual contract terms to them prior to booking. The easiest way to do this is to mention the contract in your listing's description, and include the terms in your message thread with the guest.

Airbnb can't help enforce any special policies in your contract.

If you ask a guest to sign a contract that they weren’t notified about before they made the reservation, they can decline to sign the contract and ask you to cancel the reservation instead.