Thank you very much!
That seems to be promising.
Before I buy an adapter it would be good to test the display if its still working etc. Furthermore I want to include the display in a project where I directly use an ATMega328 in the future.
Is there any wiring/schematic and/or library tutorial that I could test before?
Edit: I found this pin schematic: http://www.bustatech.com/wp-content/uploads/2014/12/pins.png
Connecting pin 19 to 3.3V and pin 1 to GND activates the background light. So this could be the pin setting! 
I will try this pin setup. Maybe I get it working.
Is it save to try opperating this also on 5V logic?
Thanks!