How would I make a race checkpoint system?

--Spiyder1

local Part = script.Parent

while true do
    if workspace.Start.yes.Value == true
    then
        script.Parent.Transparency = .5
        script.Parent.lastheck.Value = true
        wait(.001)
    end
end

while true do
    if script.Parent.lastheck.Value == true
        then
            local function PlayerTouched(Part)
            print("hit")
            script.Parent.yeso.Value = true
            end

            wait(.001)
            Part.Touched:connect(PlayerTouched)
end

There's the code, I want to make the game see that a player hit a checkpoint so the player can continue the race normally (think vehicle legends racing) but the second checkpoint doesn't appear and I have no idea why. No output errors

(P.S. o at the end of the name stands for one)

Let me know if you have any questions about anything about the code! Thanks!