Screen doesnt work after battery replacement

After I replaced the battery of my ipod nano 3 the only display like a white color.

Everytime I reset it, it makes two beeps after starting. I tried resetting via iTunes, the iPod itself and getting into the diagnostics mode. I can hear the iPod making click sounds when I use the buttons. I checked the display ribbon cable multiple times and made sure it is properly stuck in there.

I afraid I fried my screen because I can´t disconnect the battery before connecting the screen since it is soldered on. Do I need a new screen or is a connectiong loose?