Can I send you my iPod to fix it?

bichunaaa bichunaaa , the very first issue that you need to deal with is the "water damaged partly screen" This model iPod is a bit of a pain to work on. The iPod Nano is a habitual trouble maker with the back light. I know that the 4th and 5th gen are some of the worst ones. Use these guides to work on it. Now, the backlight is actual part of the LCD that may need to be replaced,but the inverter circuit is on the logic board. I have never managed to isolate the coil that is responsible for most failure on the Nanos. To clean the cable and all the connectors and clean the logic board with isopropyl alcohol as outlined on hereAlso, with any submersion, you do want to change the battery as well. If the backlight coil on your logic board got short circuited, that may require a new logic board. If none of this works for you, You may just have to replace the logic board. Hope this helps, good luck.