How do i make a temporary speed change script for robux?

I am working on a script for Changing a players speed for 180 seconds (3 minutes) that is bought with a developer product so i has to be bought over and over. Here is my script for buying the product:

local productId = (Id goes here) -- change to your developer product ID
local player = game.Players.LocalPlayer

script.Parent.MouseButton1Click:connect(function() --DONT CHANGE THIS
	Game:GetService("MarketplaceService"):PromptProductPurchase(player, productId)
end)

I have the script for changing the speed here:

if local player = game.Players.LocalPlayer ProductPurchase = true then
local player = game.Players.LocalPlayer.Speed = 20
wait (180)
local player = game.Players.LocalPlayer.speed = 16
end

If i combind them like this:

local productId = (Id goes here) -- change to your developer product ID
local player = game.Players.LocalPlayer

script.Parent.MouseButton1Click:connect(function() --DONT CHANGE THIS
	Game:GetService("MarketplaceService"):PromptProductPurchase(player, productId)
end)
and if local player = game.Players.LocalPlayer ProductPurchase = true then
local player = game.Players.LocalPlayer.Speed = 20
wait (180)
local player = game.Players.LocalPlayer.speed = 16
end

Would that work or is this script broken really bad?

This might work, but the wait time might be too long. If this doesn't work, you should probably try to use a button press, like Shift.