Please help me on designing an ER for the following scenarios..

* Guest do a hotel reservation
* Handling the billing part for the activities that the guest does during his\her stay @the hotel

Your help will be greatly appreciated, if anyone can help me...

Attached is an example of the tables and relationships between the tables you can use to get you started. You will, of course, have to add the fields, but I think the tables and relationships should work for the main database structure.

what about if the hotel accepts multiple reservation how would you do that in database
thanks

What do you mean by multiple reservation? Do you mean if one person reserves more than one room?

In that case, there will be 2 Reservations records with the same Guest ID but different Room IDs.