"Alternativkultur" in Germany is something like the "counterculture" in 1960s America -- hippies, radicals, artists, bohemians, activists, squatters. That sort of thing lasted longer over there than it did over here.
similar in motive to the notorious car-b-q's of France within it's 762 no-go zones (muslim gangs).
That's a toughie. It can be hard to separate out the actions of an underclass that happens to be Muslim and something explicitly and professedly Muslim.
What's been going on in Berlin and Hamburg has been attributed to different origins, though I haven't seen any hard evidence one way or the other.
What could have started with anarchists and activists may have spread far beyond politicized circles.
Berlin-Kreuzberg is considered both an "alternativ" area and the "Turkish" district, so if there is ideologically-motivated or recreational car-burning going on among young people, some Muslims are bound to be involved, without the burnings necessarily having a religious or ethnic motivation.