Moving from XML and .txt to Core Data

[Parental]

Hi I wrote an application, already published into the store, about driving school test, I think it is great but I'm not happy with one thing: performance.
For now I'm reading the list of questions from a .txt during the launch of the app and I save them into an NSArray but it takes so long, at least 30 secs.
Also, when a user answers to a question I store the answer and other data into a XML file, but when it contains a lot of data of course it's a pain to read it.

So I'm thinking to move to SQL or Core Data but I wonder if there is something to easily port from XML and .txt and for you will i see some performance improving?

Sorry for bad english