how to delete music app from my Mac

Reinstalling the Music app doesn't cause music in the app to be reindexed. When you say things are missing do you mean that content that was previously listed in the library no longer shows up, or content that you have won't play because Music says it is missing? Different advice for each scenario and it would be unwieldy to post both.

tt2

None of the Apple apps installed with MacOS can be removed from the Mac because they are installed on a read only partition, sealed on your Hard Drive, and there is no Music app available to be installed again in the Mac App Store.