From The Independent Germany to tighten rape laws in wake of Cologne attacks, but a search for Google News of "rape Germany laws" also gives matches for The Daily Mail, and Russia Today:
Currently, victims must prove they resisted physically and verbally, in order to prove that they have been raped
Currently, Germany’s rape laws only include attacks where a victim can prove that they physically resisted and also verbally said ‘no’. If a victim freezes out of fear, is unable to consent due to drink or drug intake, or resisted but cannot prove that they did so, their attack does not meet burden of proof standards in the German legal system.
It cites an article by TheLocal.de "Germany tightens rape law in wake of Cologne assaults".
Wikipedia's article Rape in Germany talks about the history of rape laws in Germany, with the latest legal update being from 1997, and has no mention of victims having to physically resist their attackers.
Did German law, until recently, require rape victims to physically resist their attackers?
Update: The laws were changed in July 2016. From the BBC: Germany rape law: 'No means No' law passed