I visit the Facebook group "Lust auf Wiesbaden" most often. There I find out what's going on where I live (politically and in terms of events), keep in loose contact with acquaintances and expand my local circle of friends. Occasionally I also get into conversation with people here who I've known by sight for a long time and would never have spoken to. We then arrange to meet up in "real life" from time to time.
Of course, I also use the group to distribute information. For me as a couch potato, home office worker and volunteer, all of this is equally important.
The group operator (a communications colleague) uses this group very instagram data successfully as a PR and marketing tool. Topics discussed in the group even make it into the local press.
I don't use Facebook that much for work. I do check out work-related groups from time to time and post occasionally, but I always find that my virtual copywriters' forum is much more useful to me. (Not just for work.)
So far, I haven't been able to find customers in FB groups. But that's probably because of my topics. Simple language and CSR communication aren't that common in Germany yet.