What is important is that you remember that this is a walking tour and you therefore need good shoes to cope with the distances and the cobblestones. I recommend that you have waterproofs and an umbrella on hand - Berlin is not typically a wet city but these days you never know. The "Open Spaces" tour only takes place when it is dry (there is a reason why I left the UK!).
You can take these meat-free tours in English, French or German. English is my language mais je parle aussi français und wenn Ihr Deutsch hören wollt (freilich mit Akzent), dann kein Problem!
Come relaxed and open-minded and hungry of course!