3 questions in this topic.
Access right level for each function can be found in Administration > Access Rights. Define here how many admin stars is required from user to access a certain function. Users sta...
To allow a user to log in to the admin system requires admin rights which you can define on their user accounts. The amount of stars defines the admin access rights.
Check that users admin user rights (stars) matches with the settings you have defined in Administration > User Rights > Create booking.