the interview is in 2 days. On the first one there is a group interview where they basically check if you are able to turn on a computer and digit on a keyboard, after that they check your English level with some written test. You don't need a great English level. Being able to read and write is far enough. They can use iMac computer so be prepared if you never used. On the second day there is a personal interview which could be in English but usually the recruiters are not a native speakers and often they speak a very bad English so that's not a big deal.