Unfortunately it's mainly German sources. I hope Google Translate can help here. They may also report different numbers, depending on who would be included in "Turkish migrants". Some address Turkish citizens (who have a work permit in Germany), some address German citizens of Turkish descent.
The numbers I used are from this article:
https://www.taz.de/!5176721/
> 75 Prozent der Migranten türkischer Herkunft haben keinen Schulabschluss, fast jeder zweite ist arbeitslos.
> 75 % of migrants of Turkish descent do not graduate from school, almost every second is unemployed.
It's from 2008. Upon reflection I would expect that the situation is not as dire anymore, due to Germany's positive economic development.
In any case, the trend in Germany hints towards a dire situation in any case (2009):
http://www.spiegel.de/international/germany/immigration-surv...
> Some 30 percent of Turkish immigrants and their children don't have a school leaving certificate, and only 14 percent do their Abitur, as the degree from Germany's top-level high schools is called -- that's half the average of the German population.
This article from 2016 references a report from the Federal Statistical Office of Germany. It states that over 40 % of the Turkish immigrants and their children only achieve a very basic school leaving certificate ("Hauptschulabschluss"). With this type of certificate, it is difficult in Germany to even get into a vocational school. Also, over 1/3 of the Turkish immigrants are poor: They earn less that 60 % of the mean income.
https://www.welt.de/wirtschaft/article155700942/Warum-so-vie...
https://www.destatis.de/DE/Publikationen/Datenreport/Datenre...
Out of the 3 million Turkish migrants in Germany, 275,000 have received unemployment benefits in 2015. Only people actively seeking employment are eligible for those benefits. I could not find the absolute number for Germany for this population. But for the whole of Germany, we have 39 million workers, out of a population of over 80 million. The Turkish migrants tend to be younger, so a larger percentage does not belong to the workforce yet.
I would therefore assume that the unemployment rate is around 20 % for Turkish migrants in Germany, and considerably higher in Berlin, due to the "special" economic status of Berlin as a whole. The article below is from 2001 and has them at 42 %:
http://www.tagesspiegel.de/berlin/tuerken-in-berlin-beruf-ar...
Summing up, while the specific numbers should be subject to scrutiny, the trend remains abysmal.