So Berlin has a problem with gangs of Palestine/Lebanese background, especially around the area Nordneukölln/Sonnenalle. But if you look at the history, the issue is nearly entirely of german making - and the voices from the liberal left had been warning a long time that things would end up this way, if the convervative policies would continue:
A very large part of those people or their parents/grandparents came to Berlin during the Lebanese Civil war, or due to the Intifada in the time between 1975 and 1990. They‘d travel to Eastern Berlin and then take the S-Bahn to the West - that was easy, there were no border controls. Because having border controls on the West Berlin Side would mean acknowledging the border, and thus the GDR, and that was politically undesirable. And once on the western side, they‘d apply for asylum. Since they were fleeing a war zone, and not be classified as politically prosecuted, they‘d not get full asylum, but deportation into a war zone was prohibited by the Geneva refugee convention (Duldung, in german legal speak)
Now, they‘d have a grey zone status - no asylum means no social security, no work permit, no legal status. The only ways to earn some bits of money were illegal jobs. They were deliberately marginalized and kept at the fringes of society. There were no offers that would help them integrate into the German society, no language classes, schools and childcare would try hard to keep the kids out - which was legal, because their status implied that school wasn’t mandatory for those children. This changed in 1990, when school became mandatory. But instead of placing these kids in schools where they‘d receive suitable education, the Berlin Senate kept the schools underfunded and after the reunion staffed them mainly with teachers from East Berlin (those were public officials and could be ordered to teach wherever the senate wanted). Unsurprisingly, teachers with GDR education in an underfunded school in a school system that was new to the teachers were not well suited to deal with the task at hand. The entirely predictable result: Many pupils left without a proper education that would give them a chance on the labor market.
To make matter worse, the CDU (conservative) senate in the 1980ies primarily funded religious conservative groups in the Lebanese/Palestine expat communities - with the intention that they‘d strengthen the bond between the expats and their home culture and countries. Instead of rather funding the liberal non-religious groups.
Fast forward to now: We now have people in their sixties and seventies that came as young adults, never had a legal permit to work, their kids with no real chance at even basic eduction, all grown up in poverty, the third generation kids, grown up in a dysfunctional implementation of a school system, all of them deliberately marginalized, and at the same time being influenced by religious conservative groups supported by the government.
It is objectively true that we have a problem there. But it‘s been a long time coming and it stems to a very large extend from not acknowledging that these people exist, that they need to be given a chance to integrate because that would, as a first step, require acknowledging the fact that they are here to stay.
This is the Berlin example, but if you look at how the entire debate around the Turkish „Gastarbeiter“ went in the 1980/1990ies, the same pattern is visible.
See https://taz.de/Debatte-um-Berliner-Sonnenallee/!5965454/ (German), plus the documentary linked in the comments to the article and further reading mentioned in the article.