İf I were you, I would study any time everywhere, this is not only about the Ryan air, maybe you don t have to be perfect but at least you should explain exactly what do you think. mostly, English not main language for people in the word. however English is the main language around the world. you can watch English movie, serial movie, aircraft investigation (especially national geographic) read about the aviation books. I m totally sure you will develop day by day then you feel ready for every interview.
Good Luck!!