help me fix this ?

1 this script i am trying to make it so you can buy it with robuxs

local player = script.Parent.Parent.Parent.Parent.Parent
local DevProductScript 
local tool = game.Lighting:findFirstChild("Desert Eagle") 

function picture() 
script.Parent.Parent.Picture.Image = "http://www.roblox.com/asset/?id=54706123" 
script.Parent.Parent.DevProductScript.Text = "1" 
end 

script.Parent.MouseButton1Down:connect(buy) 
script.Parent.MouseEnter:connect(picture)

2 is i made a deve thing but i cont mix it whit that to make 1 whoe thing working

local productId = 20415401 -- change to your T-shirt/gamepass ID!
local player = game.Players.LocalPlayer

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