Convert Offline to online game

Hi guys, I'm a newbie in Unity, I have a single player offline 2d game, I want to make this game an online game.
It should work like, 2 players join a match. The first player that finishes - for example- a Candy crush match. Wins the match.
Should I need to create the same game again just for converting it online?
I Guess I will need to only pass some variable between the match.
Also, I downloaded the Photon's PUN to make it work, And I need to multiscene…
Thanks.