How do i make it so something happens like a function for when people respawn?

You need to use the CharacterAdded event . You use it like this:

game.Players.PlayerAdded:Connect(function(player)
    player.CharacterAdded:Connect(function(char)
        -- This code will fire when player respawns...
    end)
end)

For more reference, you can see this:

https://developer.roblox.com/en-us/api-reference/event/Player/CharacterAdded

Hope it helped