Trashed songs are not gone. They go to the Trash smart folder in your library.

 

On iPhone, iPad, and Android, tap Trash, find the song, and restore it. On Mac and Windows, click Trash, open the song, and choose Restore on the banner across the chart.

 

A deleted playlist cannot be recovered, although its songs can. If you are about to try something drastic, duplicate the playlist first.

 

For more, see Organize your songs into playlists on the iReal Pro website.