DataStore in UML Class Diagram

1. Placing login method in the class which gains login does not seem to be reasonable. Authorization should be a class of its own and a user may gain access through it.
2. There is nothin modeled which shows the occupation of rooms. I'd expect some Occupation class which links rooms to time ranges.
3. The same. What is the basis for the occupation? There needs to be an Occupation class which relates Room with time frames.
4. What are marketing purposes? You could implement some user statistics that traces when a user has booked rooms, how punctual he paid, etc. Those are not modeled.
5. Since you have not modeled a Reservation you will not be able to cancel it.
6. The Payment is related to nothing. So you don't know for what a payment was made. Your book keeping will love you for that :-(
7. As above: no reservation modeled - no modification possible.

You should probably find some mentor to sit together and do some basic modeling.

Edit (as on the updated model): This is not the way to go. The datastore will serialize the single objects, and not be a class of its own. The way you need to do it is to construct a model with the relevant classes. Those will finally result in persistent objects in the database. FacilityAvailed does not look sensible. This looks like information you can compute from Reservation (which needs a relation to Room which is now missing completely). Well, you should dump this approach and start all over. Just model the business objects (BO): Room, Reservation, User, Payment, etc. Relate those meaningful. What are the attribute of each BO (Room: Number, Size, Cost,... User:Role, Name, ...). Then try to relate them. E.g. a Reservation may relate Room and User, but could also be simply for refurbishment/cleaning etc.