EDIT2: I got the Audio-MIDI-Setup working with configuring ALL 6 5.1 Speakers! I had to connect the colours in totally wrong jacks: green to green (out/no change), black to blue ("in"), orange to pink ("mic in"), all six speakers could be checked individually - don't know why this works.
EDIT: After restarts (and putting english as the primary language) I got some Audio again, all three ports for line-out are recognised, but using Audio MIDI Setup and 5.1 doesn't put any noise out of the speakers, except 1/2 (and even 2 now is very weak; before in Stereo, they were both equally loud). S, at least I have some Stereo.
Install audio again: MultiBeast 9+ > Drivers > Audio > RealtekALCxxx √ ALC889 only
Thanks, toleda, for your input. Sorry for having been so impolite recently - my frustration over not being smart enough for setting up a mackintosh should really not be an excuse, but sorry.
I tried to install ALC889 only, but lost Audio again. Not sure why. I also used the migration assistant (from a chimera 2.2/MacOS10.95) just before and had difficulties to get it running again. So many things perhaps not compatible. Now Sierra is running, all files (except computer parameters) migrated, BUT loss of Audio.
Attached, what I was able to save as pdf (System information Audio). I guess, there should not be "Audio ID 2"
(the input channel is from the webcam, i.e. nothing from ALC889 is recognised)