Germany has many places, where you can eat on large tables and meet new people. It might be a little to cold for the beer garden (and frankly that's not what Berlin is know for), but there plenty of bars, eateries you'll be happy.
Go local and you'll meet potential new friends.
(I did that in Tokyo. I did go to Izakayas and small eateries, sat down next to locals (which coincidentally spoke English), got help ordering food and had brief conversations. It was simply fantastic).