@Julia2556
Options:
1. The guest first need to sent an inquiry on the listing, to make the "special offer" button show up, so you can sent the offer.
2. Setup the offer in the calender (manually pricing of dates) or in the listing (extra discount or fixed price for specific weeks/months) and ask the guest book when ready.
3. Let the guest book at normal price and use the "change" option to amend the price in the changeform to that of the special offer.
Please note 6 weeks is a "long term stay" (LTS) with the LTS cancellation policy attached.