I could solve several other issues with my laptop thanks to this forum. The only thing I can't figure out is the non working FN-Keys for the brightness. Volume control is fine.
Two things I found out so far:
1) I might have to update my BIOS (would only work in windows and I'm running 14.04 Ubuntu only)
2) I have to "re-program" every key myself, using this "recording" function in the Terminal, unfortunately I send my laptop to sleep when I press F4. And anyway this option seems very complicated.
Thanks for your help!