In Music, select Songs from the left menu bar. Choose File > Library > Show Duplicate Items. Browse and delete duplicate items.
Why am I getting duplicate songs on my iPhone?
iTunes or Music may create duplicates if the same content is repeatedly added from outside the media folder when it is set to make copies of anything that is added to the library, or is added from an external drive that hosts the media folder if it was offline when iTunes or Music was launched.
Why is my song repeating on Apple music?
Open the Music app and tap the Now Playing bar at the bottom. When you see the song that's playing, tap the Up Next button on the bottom right. Tap the Repeat option to turn it off. If it's set to Repeat, tap it twice, and if it's set to Repeat 1, tap it once.