How can convert audio files to lower bit rate in iPod?

You'll need to unsync the music that is currently on the iPod and sync it again with the new settings.

Connect the iPod to your computer via USB and select it in iTunes. Select Music. Unselect any check boxes, then unselect the Sync Music option at the top then click "sync" in the lower right. That ought to remove all the music from the iPod. Once that is finished reverse the process.

Ah, since you have "manually manage music" selected the process is different.

Highlight the iPod then select "Music." Click in the music list, select all the tracks (CMD+A) and press the Delete key on the keyboard then the "remove" button.

Once all the music is removed from the iPod you can drag-n-drop new music and it will all be cross-converted.

NicoxDJ wrote:

But then i will lose my playlists :/

They are in iTunes.

NicoxDJ wrote:

Nope, they are in my ipod only:

???
How did they get onto your iPod?

Scroll down on the left side of iTunes and they should be under Playlists (shown at the bottom of Sidebar).

How did

In iTunes, select the playlist on the iPod, right click - Export playlist.

Save it to the dektop.

Then in iTunes. File > Library - Import playlist and select the playlist you saved to the desktop.

Do this for all playlists on the iPod.

You can then sync these playlist back to the iPod.

Select the iPod the Music tab at top and Sync selected playlists.

You can add/delete from these playlists in iTunes then resync to change the content on the iPod.