Will my music be deleted?

I bought a new laptop (HP laptop) over the Christmas holiday and after syncing my iPhone XS Max (the phone has the latest updates) to iTunes on the laptop, it erased all my music that was downloaded from CDs off of my phone. After weeks of importing the CDs to iTunes on the new laptop and then saving them to a flash drive (so that if this happens again, I don't have to re-import again), I still found that my iPhone (whenever it syncs to iTunes on the laptop) would delete or add songs without me doing it. I found that I had to turn on the option for me to manually sync the songs myself. Even with this option on, I still find that if I delete a duplicate song or a song I just don't want anymore on my iPhone, and as soon as I plug in my iPhone to my laptop with iTunes, the songs in question will be readded to my music library on my iPhone. The songs in question were still on iTunes at the time. I have since deleted my entire music library from iTunes because it was taking up too much space on my laptop. I got more CDs I want to import to iTunes but I am afraid that the second I plug in my iPhone (to sync the new songs), it will delete my entire music library from my iPhone. Even though I have the option to manually add/delete songs on iTunes. Unfortunately, the previous laptop I had broke and I never had to delete my music library, I, unfortunately, bought a new laptop with may less memory on it so I can't have too much music saved before it asks me to clear space. I am stuck with this laptop but I don't want to be put into this situation over and over again. So is there any way I can stop iTunes from deleting my entire music library every time it syncs my iPhone? Or do I have to deal with this because there are no options for me? I have not tested this theory of plugging my iPhone into my laptop with iTunes running in fear that it might mass delete my music library. I am hoping there are options for me so that's why I am asking here. Thanks!