How to limit appointment time only to 30 minutes?

1. The default appointment slot duration is set in "backend_create.php" file using $slot_duration variable:

$slot_duration = 60;

You can change it as needed.

2. Yes, you should change sesion_id to user_id. This demo project doesn't implement user authentication. But the logic requires user identity - so it uses session id to simulate it.

Thank you, for your reply.