@Alexey77 Your Booking and Airbnb calendars are synched.
When someone actually requests a booking on Airbnb, the date is automatically blocked. If you needed to block it yourself, then the guest only made an “Inquiry”. Open the date back up and the potential guest, or anyone else for that matter, can make an actual booking when they are serious.
It’s not good practice to block dates for anyone while they “decide” what they want to do. They may decide against booking with you, and in the meantime you miss out on other bookings.