So there is no calendar in which I can mark red for booked dates,
like on other booking sites, for example Airbnb or Booking.com
or in WP booking system: https://www.wpbookingsystem.com/tour/
You did not explain how, after reservation is paid,
I can manually close occupied dates…
After guest book his dates, his reservation is I suppose under pending
reservations. After I receive payment I have to somehow manually mark
that reservation as booked or reserved. System of course cannot do it by itself.
For WP booking system that is very easy, check here:
https://www.youtube.com/watch?v=Nn1HVpeBGI0
Please explain how that can be done in your system.