Chosen Solution

why the memory seems to be full and only i can get to listen 8 songs?

Try a Hard Reset of the device and re-sync with iTunes.

in iTunes, select your iPod or whatever the name of it, the go to Summary. Check “Convert higher bit-rates to 128kbps AAC” the reason for this is that there are songs that are higher in bit-rates that are in higher quality, meaning wasting of memory.