I need a command block where if you step on it, then it starts a timer for 15 seconds and says in chat "The crown has been picked up!", and if the person who stepped on it dies then the timer stops. Also, when the 15 seconds are up it needs to set off fireworks. Also - the timer should stop when the player who set it off dies, if that's possible.
I have had people explain each command, but I don't know how to mesh them together in one command block since I am pretty bad at them.