tess firstly, German efficiency is a myth 
Secondly, the NRW police chief was sacked shortly after NYE due to failings in policing around that time. It has been a big problem, beginning last year with some far right riots that completely caught the police by surprise and culminating in NYE.
The main issue hasn't been migrant crime but far right crime and the inability of the police to deal effectively with that. One of the issues has been that Germany is very, very unwilling to breach an individual's right to privacy so things like stop and search etc aren't really known here, or require a much higher bar of suspicion of wrongdoing (it's actually part of what contributed to the Germanwings disaster).
That's my localised view anyway. I admit I don't have a huge handle on what happens nationally because although I speak the language I'm not fluent and find the broadsheets and news programs difficult to follow. I also find that although I can understand what they are saying, "capturing the mood" and understanding cultural references is really very difficult although I've been here over ten years.
Shock horror, I haven't fully integrated!! 
So you see why I might be more understanding of the difficulties that migrants might face adapting in the uk than someone whose experience of the "other" doesn't extend beyond a week in Spain 