SQlite to store data on Core Data with a Web service that responds XML

I'm new to swift and I need to make an application to communicate with a Web servise responding XML.

1. XML data need to store them in the application so that it can operate without internet.

2. the data can be edited (no internet).

3. echos changes locally debaeran uploaded to the server.
4. if another user makes changes to the server list must be updated on the phone to get the updated data

I need help figuring out how to do this. not how to use Core Data or SQLite I need help please.