For the program itself: not required but very helpful. Most ISME courses are taught in English, but some courses in disciplinary programs are in German, and some secondary literature you'll encounter is in German or French. Having at least reading knowledge of German opens up more course options.

For daily life in Berlin: English works in many contexts, especially in the university environment and international neighborhoods. But many bureaucratic processes (registration, bank accounts, housing contracts, health insurance) are easier with German. Not all doctors, landlords, or officials speak English. Learning at least survival German will make your life significantly easier.

FU offers German language courses you can take before or during the program. See the Starting page for resources.