Use the "Photon 2" unity plugin for your multiplayer game
It is easy to use and there are alot fo videos online

https://www.photonengine.com/pun - The multiplayer engine
Here is an playlist that explains EVEYTHING (the basics and a little more)
about the Photon plugin:
    https://www.youtube.com/playlist?list=PLkx8oFug638oMagBH2qj1fXOkvBr6nhzt

No of videos : 27
Average length of video : 9 minutes, 37 seconds
Total length of playlist : 4 hours, 19 minutes, 42 seconds