I am currently designing the class diagram for my Hotel Booking application. The way my teacher said is to derive 5 base use cases from my use case diagram and then use those to make up my class diagram.
I have made my use case diagram (it's gonna be an application like AirBnb), but i'm struggling with the class diagram. I feel like it is not detailed enough. Also i am not allowed to use an interface in my class diagram because class diagrams usually represent the backend and data models of the system. Below attached are my use case diagram and class diagram. [My class diagram](https://i.stack.imgur.com/azvyJ.jpg)
Could you tell me what things are missing in my class diagram, and also what to use instead of interfaces in it?