Hello ines-ave,
Thanks for using Apple Support Communities!
We understand you are seeing duplicate entries for a playlist you created in Apple Music and want to remove them. We are happy to help provide some assistance with this.
If you wish to remove playlists from Apple Music, just open Music, select the playlist you wish to remove, then press the 3 dots next to the playlist name, then choose the option to delete. Take a look at the steps listed in this helpful article:
Delete music, movies, and TV shows from your device
Specifically the section titled "Delete music and music videos".
You can also see some helpful steps listed here on creating playlists within Apple Music:
Create and share Apple Music playlists
If this issue is common or continues to happen, we would like to ask some questions to better understand what might be happening.
1.) Does this happen with multiple playlists you created, or is this the first time this has happened?
2.) Did you use iTunes to sync the playlist to your device, or did you create that on your device?
We hope this helps!
Best Regards.