Proficiency in german language is a hard requirement for all new hires and only if they are in dire need of experienced crews this will be waived (on a case by case basis). Experienced in that case means probably generally high time, lots of widebody hours and B777 rated with lots of hours on type but this is pure speculation from my side as i'm not involved in the recruitment process.
Concerning the selection process, expect the usual array of aptitude and psychometric tests, a simulator evaluation and an interview.