The problem is that German mainstream media is not covering these topics
Well English media don't seem to provide any proof for the original claim either.
Your first link shows a picture of a lady with a “Jews against genocide” sign flanked by two police officers.
I see no arrest and at least at that moment in time she is still allowed to show her sign.
Link two contains these passages:
Her banner, which said she was ashamed to be German and that there was a “genocide” taking place in the densely populated Palestinian enclave being bombarded by Israel.
Police let her and her sign go, and she joined the march.
At about 4pm, police pushed into the crowd and, to calls of “shame, shame”, pulled Monika Kalinowska out.
Her sign, written in red, read, “Israel is a terrorist state.”
After she was frisked and her identification checked, she was told there was nothing wrong with her sign – even though it was confiscated – and she was allowed to leave. She could pick up the sign the next day, police said.
Again, I'm not defending police here but the claim was that people were arrested, so I want to know who got arrested and for what?