How do I make this unlock next level system?

Im making a game that has different levels to complete. I want a teleport part (which I already have) that can turn a GUI invisible in a different game when teleported to that game.. Anyone know how I could do this? What scripts should I add to what? should it be in the game with the gui or with the part? my game teleport script:

local TeleportService = game:GetService(¨TeleportService¨)
local gameID = 4773204734

function onTouched(hit)
local player = game.Players:GetPlayerFromCharacter(hit.Parent)
if player then
TeleportService:Teleport(gameID, player)
end
end

script.Parent.Touched:Connect(onTouched)