BTW, can anyone give me a quick and easy guide of how to make a playlist and simply put my song into it ? I just can't stand how complicated it is for rockbox....
I covered how to make playlists in Foobar2000 in a post here:
http://www.head-fi.org/t/803844/rockbox-xduoo-x3/870#post_12978254
Otherwise, you can create on-the-go playlists pretty easily.
Make sure the player is stopped (not paused--while it's playing, tap the power button to stop playback).
Navigate to the first file or folder you wish to add to your new playlist.
Long-press Play to get the Playlist context menu.
Select Current Playlist -> Insert
Repeat steps 2-4 to add more songs/folders.
Save the playlist (remember, I said you can "create" it easily...saving is different):
On the While Playing Screen, long-press Play to get the Playlist context menu again.
Select Playlist -> Save Current Playlist
.....and now (sigh) the Rockbox keyboard.
Prev/Next will navigate the cursor left and right.
Option (the center button) will move the cursor down, and it will scroll to the top after the last line.
When the File Name field is highlighted, use Prev/Next to move the cursor, and Back to delete the preceding character.
Fiddle with the file name until you're sick of it.
Don't delete the .m3u extension.
Once you've compromised on a file name, highlight the File Name field and long-press Play to save your playlist.
IIRC, the playlist will automatically save in the root of the SD card, so you may need to copy it to your Playlist folder.
I've been using Rockbox for ten years, so I'm used to it and it makes sense to me, but I know it's not easy to adapt to.