I was very nervous at the beginning, but they do their best to make you feel comfortable. First round interviews consisted of about 5 min talking about my resumé in English, and then we procceeded to the case question. Bain is known for its mostly quantitative case questions, and so they were. For both cases, the interviewer asked "qualitatively speaking, what do you think we should examine first to get to the root of the problem?". After that, came the numerical questions. One was a market sizing one, featuring a very difficult geometrical interpretation of a hypothetical age structure diagram (even though I have an Engineering background). I got dismissed at the very first round.