Switching from Unity Networking to Photon Networking

Hello all. Recently I got project with complain that game is crashing if one of the players decides to quit from the game or if one of the players gets lost internet connection. When I opened project I understood that it made with Unity Networking and there is an asset "Unity Networking Lobby" has been used. So it's a little bit hard for me because game logic uses some components which comes with Lobby Asset. I have done only with Login/Register/Photon Connection/Menu/Awaiting Lobby Panel/ Join Room/ Small count down lobby timer. Further game logic is hard for me to convert because I have never worked with Unity Networking Before and my Photon knowleage is also not perfect. So it will be great if there is anyone who can help me with my project. I can post all codes here or pm. Thanks in advance.