How do I make my InventoryGui disappear when my ShopGui appears?

I've been trying for about 30 minutes just to solve this simple problems. The problem is in the Inventory Code section because before, it worked without it. This is the code that I have been using:

----------Title Screen Code----------

wait (0.5)
local TitleScreen = game.Players.LocalPlayer.PlayerGui:WaitForChild("TitleGui")
local TitleFrame = TitleScreen:WaitForChild("TitleFrame")
local TitleButton = TitleFrame:WaitForChild("PlayButton")
local TitleText = TitleFrame:WaitForChild("TitleText")
TitleScreen.Enabled = true

game.Players.playerAdded:connect(function(player)
	TitleScreen.Enabled = true
end)

TitleButton.MouseButton1Down:connect(function(player)
	TitleScreen.Enabled = false
end)

----------Shop Code----------

local ShopScreen = game.Players.LocalPlayer.PlayerGui:WaitForChild("ShopGui")
local ShopFrame = ShopScreen:WaitForChild("ShopFrame")
local ShopButton = ShopScreen:WaitForChild("ShopButton")
local ShopScrollFrame = ShopFrame:WaitForChild("ShopScrollFrame")
local ShopBack = ShopFrame:WaitForChild("BackButton")
ShopScreen.Enabled = false
ShopFrame.Visible = false
ShopButton.Visible = true
ShopScrollFrame.Visible = false
ShopBack.Visible = false

while TitleScreen.Enabled == true do
	wait()
end

if TitleScreen.Enabled == false then
	ShopScreen.Enabled = true
end

ShopButton.MouseButton1Down:connect(function(player)
	ShopButton.Visible = false
	ShopFrame.Visible = true
	ShopScrollFrame.Visible = true
	ShopBack.Visible = true
end)

ShopBack.MouseButton1Down:connect(function(player)
	ShopButton.Visible = true
	ShopFrame.Visible = false
	ShopScrollFrame.Visible = false
	ShopBack.Visible = false
end)

-----------Inventory Code----------

local InvScreen = game.Players.LocalPlayer.PlayerGui:WaitForChild("InventoryGui")
local InvFrame = InvScreen:WaitForChild("InvFrame")
local InvButton = InvScreen:WaitForChild("InvButton")
local InvScrollFrame = InvFrame:WaitForChild("InvScrollFrame")
local InvBack = InvFrame:WaitForChild("BackButton")
InvScreen.Enabled = false
InvFrame.Visible = false
InvButton.Visible = true
InvScrollFrame.Visible = false
InvBack.Visible = false

while TitleScreen.Enabled == true do 
	wait()
end

if TitleScreen.Enabled == false then
	InvScreen.Enabled = true
end

if ShopFrame.Visible == false then
	InvScreen.Enabled = true
end

while InvFrame.Visible == true do
	ShopScreen.Enabled = false
	wait()
end

while ShopFrame.Visible == true do
	InvScreen.Enabled = false
	wait()
end

if InvFrame.Visible == false then
	ShopScreen.Enabled = true
end

InvButton.MouseButton1Down:connect(function(player)
	InvButton.Visible = false
	InvFrame.Visible = true
	InvScrollFrame.Visible = true
	InvBack.Visible = true
end)

InvBack.MouseButton1Down:connect(function(player)
	InvButton.Visible = true
	InvFrame.Visible = false
	InvScrollFrame.Visible = false
	InvBack.Visible = false
end)

It also doesn't say anything in the output. Thanks for the help!