Facebook's Mark Zuckerberg understands the need to stamp out hate speech on the world's biggest social network, German Chancellor Angela Merkel's chief of staff said on Thursday after a meeting between the two in Berlin.Zuckerberg is on a charm offensive in Germany, where the company he co-founded has faced criticism for months from politicians and regulators over its privacy practices and a slow response to anti-immigrant postings by neo-Nazi sympathizers."We in Germany obviously want illegal content to be removed from the Internet. That concerns not only Facebook, but Facebook among others," Peter Altmaier said after a meeting in Berlin with Zuckerberg."My impression is that Mr. Zuckerberg understood the importance of this issue," he said, describing the meeting as "very good and constructive."Facebook's rules forbid bullying, harassment and threatening language, but critics say it does not enforce them properly. It has hired a Bertelsmann business services unit to monitor and delete racist posts on its platform in Germany.Last September, during a United Nations meeting in New York, an exchange between Merkel and Zuckerberg was caught on live microphones.She asked him about the hate posts and he responded: "We need to do some work." "Are you working on this?" she shot back in English. "Yeah," he said.On Thursday at a Facebook technology showcase in the German capital, Zuckerberg told journalists: "It's great to be in Berlin." Facebook opened a new office here last week.He posted pictures of himself jogging with a minder at the Bradenburg Gate on his Facebook page. "I was able to go for a run this morning. It's my first time running in snow in 20 years," he said.Zuckerberg announced a partnership with European research institutions in artificial intelligence (AI), beginning with the donation of four graphics processing unit (GPU) servers to the Technical University of Berlin.Facebook is testing a personal digital assistant called "M" within its messenger service that is powered by AI and can answer questions with live human help and perform tasks such as buying gifts online and booking restaurants."It was very clear from the beginning that we couldn't do this without a significant part of that research being done across Europe," Zuckerberg said of Facebook's AI research.He declined to take questions from journalists, either on Thursday or at a town hall meeting at which he will address questions from the public on Friday.