I think the “Update Time” should be looping, so it executes every second, updating the “Time Remaining” var.
To change the timer I guess you can get the remaining time, subtract the desired value (5s) and store as a variable, then you clear and invalidate de timer (You should store the Handle too, so you can manage it later), then set the timer again using the subtracted variable.
I can think in better ways to do it, If I could I’d be happy to stream via Discord.