Guys a part of SunExpress is belong to Lufthansa and other part of it belongs to Turkish Airlines.But it is based on Antalya by the time there are 2 other bases in İzmir and İstanbul.Mostly flying Germany in international also they fly to almost all airports in domestic.That is most of pilots in SunExpress are Turkish so as I known speaking German is not required.But of course it would be an advantage if you speak German but not an obligation.