First thing I did was to get root access like on my Galaxy S2, I used "Nexus Root Toolkit" which was really easy to use.
Right after booting and setting up, all my old Play Store Apps were installed and the firmware wanted to update.
OK so why not...update done aaaand shit, root is gone...needed to use the toolkit again but only the root part.
Now everything runs really nice on v4.4.2 !
Added already some extra apps, really important for me is "Light Flow" to control the notification LED and its colors per app.