So one of our readers asked us this question the other day: How do interpreters hear the next line while interpreting what was just said?
Years and years of training and they work in pairs. Real time interpreters like in the UN will have one person translating speech to speech in real time, and another taking notes, preparing relevant slides and such to help the active interpreter and they switch off back and forth to get a rest due to the intense mental concentration. The people who do this aren’t just fluent in multiple languages, they have studied years just to translate well, additional years to translate on the fly, and they also spend weeks or days preparing for upcoming sessions by familiarizing themselves with the material to be discussed, and any unfamiliar words.
They also practice when they aren’t working by watching speeches on similar subject matter as they need to practice, and translating in private. It is a very demanding job especially when diplomacy is at risk. Remember “We will bury you”? by Nikita Khrushchev. It was actually “We will live to see you buried” but nobody is perfect, even experts. It’s just very demanding.