As a German, I think language is quite important. Even though there are some courses taught entirely in English and some to a certain extent, you will have to learn German
to communicate with people and for bureaucracy stuff (and oh we love it!). You might have a chance without German in Berlin, but that won't work in other cities.
As for the requirements: Just call/Email the respective university, because education is decentralised regulations vary.
Additionally, you should check how many people study abroad as Erasmus semesters are very common and easily organised at some schools, and harder at others (in general: if its required, it will be very easy to get a place and organise everything). Also, get a flatshare. Don#t move in a dorm!