Make a custom loading screen ?

Hi, So I have two places, when it teleport to the private server, I want to make a black screen who start transparency and became more and more black (with background transparency) (for the players who will be teleported) and between the private place teleport the custom loading screen is black and when the player is to the place, the screen is black and become less and less black.

So here is the code:

script on lobby:

local function moveto_mainGame(plr)
        if plr:FindFirstChild("Settings").Playing.Value == true then
    local RS = game:GetService("ReplicatedStorage")
    local ShowBlackScreen = RS:WaitForChild("ShowBlackScreen")
    local BlackScreen = game.StarterGui.BlackScreen
    ShowBlackScreen:FireClient(plr)
           TS:TeleportToPrivateServer(3410032453,code,{plr}, nil, nil, BlackScreen)
        end
    end

local script (in replicated first) on lobby:

local RS = game:GetService("ReplicatedStorage")
local ShowBlackScreen = RS:WaitForChild("ShowBlackScreen")
local PlayerGui = game.Players.LocalPlayer:WaitForChild("PlayerGui")
PlayerGui:SetTopbarTransparency(1)

local screen = Instance.new("ScreenGui")
screen.Name = "BlackScreen"
screen.Parent = PlayerGui

local frame = Instance.new("Frame")
frame.Size = UDim2.new(1,0,1,0)
frame.Parent = screen
frame.BackgroundColor3 = Color3.fromRGB(0,0,0)
frame.BorderSizePixel = 0
frame.BackgroundTransparency = 1
frame.Visible = false

ShowBlackScreen.OnClientEvent:Connect(function()
    frame.Visible = true
    for i = 50, 0, -1 do
        frame.BackgroundTransparency = i/50
        wait()
    end
    frame.BackgroundTransparency = 0
end)

and local script in the game (in replicated first):

local TeleportService = game:GetService("TeleportService")
local Players = game:GetService("Players")
local ReplicatedFirst = game:GetService("ReplicatedFirst")
local PlayerGui = game.Players.LocalPlayer:WaitForChild("PlayerGui")
PlayerGui:SetTopbarTransparency(1)

local customLoadingScreen = TeleportService:GetArrivingTeleportGui()
if customLoadingScreen then
    local playerGui = Players.LocalPlayer:WaitForChild("PlayerGui")
    ReplicatedFirst:RemoveDefaultLoadingScreen()
    customLoadingScreen.Parent = playerGui
    -- animate screen here
   for i = 0, 50, 1 do
        customLoadingScreen.BackgroundTransparency = i/50
        wait()
end 
PlayerGui:SetTopbarTransparency(0)
    -- destroy screen
    customLoadingScreen:Destroy()
end