Furthermore, the Rütli-Schule is situated in a part of Berlin that is considered to be problematic because of the high unemployment rate, which affects both migrants and Germans alike. There is also the problem of a higher than normal percentage of school dropouts, migrants and Germans are both affected once again. As it was stated in the video you posted, many of the Neukölln teenagers don't have very good future prospects, something which is important when considering the violence. Hence, Berlin Neukölln is a very specific example that is much more complex than you're trying to pass it off as. To say that the immigration of muslim citizens is the problem is way too simplistic. And to try and use this as an example for the whole of Germany is also too simplistic.
Now, there undeniably are some problems with the integration of immigrants into German society. However, these problems mostly stem from a variety of problems concerning the treatment of immigrants. For the longest time immigrants, especially muslim ones, have been shoved away into certain districts. Now there are muslim communities in some cities that number several thousand inhabitants. The immigrants living there don't actually have to interact with Germans very much anymore. Furthermore, the future prospects and job situations of many immigrants are still very poor a lot of the times. This has to do with the fact that obtaining a right of residence or just a working permit, not too mention a citizenship, takes a ridiculous amount of time in many cases. Sometime families have been sent back to their "home countries" after living in Germany for 15 or more years. And while the process of determining the right of residence is being processed, people are not allowed to work in any way, shape or form. Now how well would you be integrated if you weren't allowed to work for 15 years after emigrating to another country. These are, in my opinion, the biggest problem concerning immigration and integration in Germany. The fact that most immigrants in Germany are muslims has nothing to do with it.
I hope I managed to give some more information on the whole Rütli thing as well as clarify some of the integration problems which Germany is facing.