there are some infos about the mafia in germany, but you can not compare it to the mob watchers in the US or the amount of information about the mafia in italy. The reason you can read this article about the italian mafia in germany is, that there was a trial in germany against some italians who are connected to the mafia.but only on occasions like this(trials,murders) this topic gets some media attention.
There have been a few murders carried out by the mafia in germany. nothing like the duisburg killings , but there were a few murders in east germany after the reunification. there was also a trial in Saarland last year about a murder with supposed involvment of the stidde. its true, that they are not acting like they do in italy, but id say, that there is at least one dead italian mafioso or one attempted murder in germany. In the past there was the "famous" case of Giorgio Basile, who was a high ranking assosiate and killer of the ndrangheta in germany. He is said to have killed up to 30 people(numbers are from his wikipedia page, but i think i read somewhere else, that he "only" killed 12 people). he became a pentito, thats why we know some infos about the inner communication and structure of the mafia in germany. there is also a biographie about him.
Bedsides the police there are only a few journalists who can be called expert on this topic. one is jürgen roth, who tends to exaggerate numbers of members(he said that there are at least 1000 members in germany) and turnover. but he still is the most profiled author here. but even roth changed the subject of his work because there isnt enough attention.recently he writes about the state crime nexus in russia.
I think the main reason why you cannot find a lot infos in the media in germany about the mafia is, that the problem with HA and Bandidos/Gremium MC etc is perceived as the bigger one.

If you have some questions i can try to answer them.