In general, non-Muslim immigrants (Italians, Poles, etc.) assimilate. Each generation accepts more and more of the culture of their new country.
But in general, Muslim immigrants do NOT assimilate. They keep their traditions, and they keep their hatred of the West. So yeah, Germany can expect these attacks to continue for decades to come.
And the left looks for excuses for more control over society. Muslim terrorism - More Government Control over resistance to violent ideology. BLM violence- More Government Control over resistance to racial violence. Occupy Wall Street- More Government Control over resistance to redistribution from workers to the lazy.. Global Warming, Government control over the means of production to have control over who wins (Solyndra) and who loses (Massey Energy). And those who make the rules are elitists who have never produced anything preying on those who are productive and who the elitists despise.
There are 2.23 million Hindu’s in USA. Some are born here, some are naturalized citizens, some are legal immigrants with green card, some are on student visa studying in a college somewhere. I am sure there are a few visa overstays as well. Considering that large number, there is not many attacks by Hindu’s on women in USA in the news. In fact you will rarely see Hindu’s committing violent crimes of any type in USA.