How do you use ScreenGUI as dialog?

I want to make it so when someone clicks on the NPC, the dialog would pop-up. However, I tried to do so but just can't do it. Here are script that I tried:

AS = script.Parent -- NPC
GUI = script.Parent.FirstTextGui --- ScreenGUI
Frame = script.Parent.FirstTextGui.FirstTextBox -- Frame
Text = script.Parent.FirstTextGui.FirstTextBox.FirstText -- TextBox
Next = script.Parent.FirstTextGui.FirstTextBox.FirstText.NextButton -- TextButton
Talk = false

AS.MouseButton1Down:connect(function(talk)
    if Talk == false then
        GUI.Enabled = true
        Frame.Visible = true
        Text.Visible = true
        Next.Visible = true
    end
end)

This is my first time coding in Lua so I need all of the help that I can get. If you could, please try to shorten down the script.