Hello @Lucrezia8,
You have to have to have a separate listing for each room.
Click on "Host" and then on "Manage listing" in the menu. Then click on "Add new listing" to add photos, description, rules etc. for each room. Give each room an individual title so guests and you will both know which one they've booked.
You can keep your current "whole house" listing if you want to be able to rent to larger groups.
If you do this, remember to keep the "whole house" calendar and individual room calendars up to date after each booking so you don't get double bookings. That is, if someone books one of the rooms for the 10th of September then that date must be blocked on the "whole house" calendar. Dates must be blocked on all the room calendars if someone books the whole house.
The link nelow explains how to link the calendars but I'd suggest checking it manually after each booking to make sure it's working.
how-do-i-list-multiple-rooms?
how-do-i-link-airbnb-calendars-for-multiple-listings?
Steve.