If you say something in chat a ScreenGUI/A timer will pop up on your screen Anybody know how? [closed]

Well, we could use the .Chatted event in this case to get the player who chatted and then do the code.

game.Players.PlayerAdded:Connect(function(p)
    p.Chatted:Connect(function(msg)
        -- code to make timer appear
    end)
end)

If you wanted it to be when the players type a keyword, you could just use an if statement checking whether msg was the keyword.

if msg == " " then -- put the keyword in the quotation marks
    -- code
end

Edit: oh ya, forgot to mention that this code might be done server side, in this case, use remote events and :FireAllClients.