Hi Tomislav, Welcome to the Community! Sadly, songs are sometimes removed from the app due to licensing issues. Evidently the license holders sometimes crack down on these things. Here’s a post from Musopia explaining a set of songs removed earlier this year. If you want to confirm that Sailing is not in the app, or have other questions, you can tag @MusopiaApps.
We’d love to know how you found us…consider heading to the Introduce Yourself topic to say hello to the group!