@Marionne2
If you cancel a reservation, the attached cancellation policy will apply and automatically calculate the refund (if any). I host can decide to give some additional refund, but is not obliged to do so.
In your case the reservation should not have been cancelled, but shortened by the host,with amending of the calculated price, so the unused nights will be refunded, including Airbnb service fees, in only one operation (to be accepted by the guest first before it is executed).
Airbnb can do not much for you, as they can not force the host to provide an additional refund.