3 interviews, one with HR, one with a lead and one with the COO. HR interview was mostly personal questions, the lead and a future colleague asked about my previous job experience, one part in German and one in English, and the COO had an open chat with me

There are three different job interviews. The first one checks your soft skills and your personality (done with HR), the second one your qualifications (team lead) and the third one is with the COO. If you pass all three, you will get an offer. They usually ask individual questions and it's definitely more a conversation than a typical interview. If you're not an English native, part of the interview most likely will be in English - at least that's how it was for me.