Normally "wofür/wozu" are used to ask about the purpose/goal/aim of an action. "Warum/wieso/weshalb" are used more broadly (e.g. to ask for the cause of some event). The English 'why' can be used to ask for the reason, the cause, or the purpose of an action. It therefore more closely ressembles "warum" than "wofür". Keeping that distinction in mind, if you use 'why' in the purpose/goal sense, it works as a translation of 'wofür'.
Ich weiß, Du weißt, Er weiß, Wir wissen, Ihr wißt, Sie wissen. (http://www.sensagent.com/alexandria-conjugation/conjugate.jsp?w=wissen=de=en=UTF-8)
This is the fourth time which I have reported mispronunciation of german words. Here she makes an "s" sound in the middle of saying "wofur". Another case is her pronunciation of "Balcon" which she makes sound like "Val - corn". Correct me if i am wrong, but the german "b" is not the same as the spanish "b". I have checked my sound system and it is good.