How do I make a timer and when it beeps we get a map?

I want a timer for my mini game and when it his zero a random map comes how do I make it?

To make a timer, you need to use a loop and make it so it subtracts every second. An example is right here :

for i=30,0,-1 do
 i = i -1
print(i)
wait(1)
end

You can change (1) to how fast you want the timer to countdown. Also change 30 to the max seconds you want in the timer