Gruess aus England !

Hello ! My name is John Richter and I have lived all my life in England but have a German father and an English mother.
My German Grandparents split up during the war. My Grandmother suffered at the hands of the Russians in post-war Berlin and escaped (with my father & Uncle) by marrying a British soldier - which is how my parents met.
My research is complicated by two things - firstly my Grandparents are dead and no other relatives have much info and secondly my German is fairly basic.
My family is mainly from Brandenburg with offshoots to Poland and possibly the Rhineland. I was also told (but have never seen proof) that one ancestor worked in the Kaisers kitchen (Potsdam ?). Just hoping to discover a little more about where my ancestors came from.