@Monika310 You can go to the Reservations tab of your Dashboard, select the current booking, and choose "Change or Cancel" from the drop-down menu. Select Change, and switch the checkout date to today. When they approve the alteration, the value of the unused nights will be deducted from your payout and the dates on your calendar will be open. You and the guest will still be able to review each other; you might get a retaliatory review so you can go ahead and start preparing the Host Response.
It's not necessary to get Airbnb involved; if you have chosen to terminate the booking, the guest is now trespassing, and if they don't accept your alteration they won't get their refund. However, you should keep a paper trail here by communicating the termination (and the reason behind it) in the onsite messaging. If they refuse to leave, don't wait for Airbnb to answer the phone - call the police.