Tizen Developers

Hi everyone,
I'm trying to develop my first native application for tizen / galaxy watch.
The purpose of my application is as follows
1) enter your username and password
2) download and save a list of items and photos (one item corresponds to a photo)


it's very simple, but what is the best technique to do it?

in particular, I look for advice on how to connect to the database and store data in the application.
A third function I want to implement is update, which is to delete the local data and re-download it.

any suggestion is welcome,
thank you