@Hannah965 You might like to explain to the guest that the service fee goes to Airbnb for providing the platform, marketing etc. As a result you cannot remove said fee but you could provide an equal discount. Its about 14.2%+vat for a short term rental.
Beware though - Guests who ask for, and receive, discounts are often known to be the worst type of guests.....
@Hannah965 Sorry I should have said the easiest way to see what a guest pays is to search the area as a guest for the days in question. It also allows you to see if you are competitive with other properties.
I’d look very hard at their profile, feedback received, given etc . I’m not keen on folks asking for discounts, they usually turn out to be trouble and the requests generally don’t stop at just the discount.
You have a lovely place! No need to discount to get guests or good reviews. In fact, I agree with @Amanda660 and @Mike-And-Jane0 that this is a guest who is exploiting a new host for personal gain. And you're unlikely to get the review you are hoping for because the potential guest is already showing a lack of respect by asking you to pay their fees. I'm not sure how that is a goodwill gesture?