Booking Cycle with Django

I have an app where the user books a session and then pay it using payment service provider (like Fawry or Paymob which are middle-east based companies). the way this is done is when the user books a session or multiple sessions a code is generated and it will be available for say 30 mins.

My Question is :

should I declare the sessions that the user is going to pay for as booked so when another user fetches the sessions they will not be available to be booked? and if so what happens if the user decided not to pay for the sessions, how would I know? and if I can know and return them back to unbooked status what if the other user that wanted them didn't check for these sessions again? OR should I make them available until the user pay for them then remove them from the available sessions, but then what if two users booked the same session -as it's not yet been removed when one user booked it-, the generated code that they are going to use has an amount of money to be paid it will not check if the session that the user paying for not available anymore.

My Suggestion :

is to make a temp table that holds the about to be booked sessions and remove them from the available sessions and after a specific period of time when the generated code is no longer available the sessions status can change back to available, but I don't know how to trigger the action that toggles the session status.

The question to reserve or not is part of your business logic an not a coding decision - so you need to decide what you want for your customers user experience.

The implementation of a reservation could be done in many ways - one simple one could be to store a "reserved_until" datetime field as well as a link to the "reserving_user" in the respective object and compare it with "datetime.now()" if the accessing user has changed.