Multiplayer system

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Im working on a demo project, where I use Unity 3D and Photon Unity network(PUN) for a real time game.

https://i.stack.imgur.com/8EEMF.png

The person in the top panel is an enemy unit, controlled by another player who does damage to the player on the bottom left (1/3 hp left). However, the person on the bottom right is a healer who can heal the bottom left player (both controlled by the local player).

Here's my problem! Since it isn't turn based and has to happen real time. How do I design my multiplayer system? Ive previously worked on turn based games, where I just pass the indices and mirror the events taking place locally, in the remote player as well.

But here with latency in the picture, I do not know how to proceed! What I would like to do is, have the healer heal the player locally as well on the remote player's phone before he is attacked by the remote player or kill the player before the healer can heal his hp depending on the timestamp in which the events happen and reflect such on both the devices.