https://t.me/AppointNowBot
(source: https://github.com/DEC1MA/AppointNow/commit/dfc19c70f24690572de0267d0a5717ce33eeb2f9)

AppointNow is a mini app for Telegram that allows users to schedule appointments and bookings. Users can also create their own businesses and receive appointments from other users. The app provides a sleek and user-friendly interface with dark mode and light mode compatibility, making it visually appealing for all users. Authentication for this app is integrated with Telegram, ensuring a secure and seamless experience.

Cool concept. After creating an appointment, the main page still says that no appointment has been set. New appointment button is not obvious when there is already an appointment. Remove button doesn't remove the entry. Labels look weird on rounded fields.

Good idea, it could be used for a real bot. I like that you've implemented a lot of backend logic, and that one can not only book apartments, but also create their own. Though, for the real world, these would most likely have to be separate bots. :)