Went I read rss from diffrent sources such as bbc, voa,... How can i plan they 'by source', 'by time',... Should I use database ? I think it make my app slowly.
Not using a database would make your app slower. Without a database every time you restart the app it needs to fetch the rss feeds from the servers. It's sensible to store the data offline and update it with the new items on startup / with a button.
Think about additional operations which need a database: labeling, starring, saving for later, etc.
This provides an additional benefit: you can store the news offline so the user can read them without an active connection.