How to transfer music from iTunes to my iPhone? - 1

So I just got a new laptop and on my iTunes I don't have any of my old music but its all on my phone. Normally when I wanted to add a song to my library I would just drag it into the iPhone, this is not working. People are saying to sync my phone with my iTunes but iTunes is saying that if were to do that it would remove all the music from my phone and replace it with what's in my library… I don't want to do that since I don't have all my music on my iTunes. Can someone please help me

Added (1). How do I download them again?

Yes, Itunes would take away all those song you have in your phone if you permit it.
Download them again. PIRATE Bay

You can follow this guide to transfer the music from your iPhone to laptop first, and then add the music into iTunes library, sync iPhone with iTunes, then you will have all the music on your iPhone.
http://www.ipod-transfer-copy.com/how-to-transfer-music-from-ipod-to-computer-itunes.html
Hope it helps. Feel free to email me if you need further help.