Playlists on iPhone App not Synced with Desktop

[thirtytwo16]

Hi. First time poster. Long time user here. I've got a weird problem, and I hope someone can help.

A few years ago, I imported a bunch of playlists from iTunes into Spotify. For some reason, I have three sets of those playlists. Oddly, none of those sets of playlists are consistent. Meaning...the number of songs in Playlist 1 are not the same as in Playlist 2, which are not the same as in Playlist 3.

Fortunately I am able to build my original playlist library by cherrypicking playlists from each "import." So not a big problem there.

However...the songs in my playlists on my iPhone do not mirror the songs in my playlists on my desktop Spotify.

I am using the same account on both the iPhone and my desktop. I'm afraid to change any of the playlists on my iPhone...where I listen to playlists mostly...with fear of losing them across everything.

Can anyone tell me how I can make sure things are consistent without losing any songs from playlists on either the device or my computer?

Thanks!