How to you script a timer, so it will show on screen?

I would like to learn how to do this is you can help then thanks! Also how do I make ALL players in First person. Examples: Deathrun and ROBLOX Battle.

About the First Person you can use this script. Whenever a player enters your game(after he/she's load) he goes into 1stPerson Only.

game.Players.PlayerAdded:connect(function(player)
	if player:WaitForDataReady() then
		player.CameraMode = "LockFirstPerson"
	end
end)

OfCourse you can change the event depending on when you want your players to stay 1stPerson Only.

Now for the timer you can have a script that every 1 second changes the text of a TextLabel and keeping the progress down, let's say Seco. If you want to add more than one minute then when Seco reaches 60 the Text changes to something like "00 : 59"