Booking.com offers a One-Way connection or a Two-Way connection.
a. Full connection (two-way): with this connection Beds24 can updates Rates & Availability and import bookings Bookings.
b. Reservations only (one-way): Beds24 can import Bookings but you manage the Rates & Availability with the Booking.com Extranet.
c. Rates and availability only (one-way): Beds24 manages your Rates & Availability but you process the Bookings with the Booking.com Extranet or email.
Please also see here:
https://partnerhelp.booking.com/hc/en-u ... el-manager
If you want to send availability to Booking.com and import bookings from Booking.com into Beds24 you will need a Two-Way-Connection. In this case Booking.com requires you to also send prices.
You will still be able to manage your promotions directly in your Booking.com extranet.