Except for a few individuals who were hired at the beginning, who came in with lots of relevant on type experience, fluency in german language is a hard requirement. That doesn't necessarily mean native speaker level but you should be able to hold a conversation
As for the company, flying gets more interesting apparently, bunch of good people there, rosters are good for the most part and make commuting possible, just know that at the end of the seniority list even with the current expansion it will take anyone lots of years to progress and all that while earning sub standard money.