Germans have a fertility rate of 1.3 children per couple. European Muslims are estimated to have approximately 3.5. Let's keep the math simple with nice round numbers:Germany is as good as gone.
Total population: 100 million.
Native Germans: 80 million.
Muslims: 20 million.
The 80 million Germans will have 52 million children and 34 million grandchildren. The 20 million Muslims will have 35 million children and 61 million grandchildren. So in two generations there will be twice as many Muslims as Germans.
Germany will probably break into smaller states. I’m pretty sure Prussia will not tolerate a Islamic invasion. And if Jean-Marie Le Pen has any say (and she will) France will act too.