All Clear.
it seems to be a little mistake of me.
the SPDIF plug was not set correct, it was a problem with the size of the plug or the case, i dont know, but it doesn't fit 100%.
But now, it works. (now you allowed to lough) and i can confirm, it works without the "dtoverlay=hifiberry-digi" line in config.txt
I think i have to work around on one of them or both a little bit, so it will fit 100% with no problems.
now i can start to understand the keymapping and try to correct it, to match the keys of my remote.
one question about this keymapping, how can i figure out, what key is pressed on my remote. Is there a addon which can show the pressed keys/key-id ?
or did someone have a suggestion, which setting is good for the Orbsmart Airmouse ?
for now, a big THANKS to all of you.