If I may, to provide a glimpse of how Europe may go as Islamic immigrant populations reach a "critical mass" in European national populations I'd like to recommend a fictional piece (Sci-Fi actually) entitled "Caliphate" by Tom Kratman, available both as paperback and e-book from Amazon.
While much of that story is centered approximately 100 to 150 years in our future, Mr Kratman lays out a probable scenario of how Europe becomes a true Islamic territory and part of a larger Caliphate starting approximately in the mid 1990's.
He postulates how that "critical mass" population is likely at around the 15% of total population mark, where activists from that minority are able to bring Europe the wonders of Islam, especially Sharia law and eventually the minority becomes the rulers because "enlightened" Europeans refuse to resist.