[DONE!] I don't care if a mod deletes this now.. Anyways HOW DO I DO THIS?

If the button is not a member of either 2 of the GUIs (meaning that it is its own GUI), you can do something like this:

-- In a LocalScript
local button = script.Parent
local plr = game.Players.LocalPlayer
local gui1 = plr.PlayerGui["ScreenGui1"].Frame
local gui2 = plr.PlayerGui["ScreenGui2"].Frame

gui1.Visible = true
gui2.Visible = false
button.MouseButton1Click:connect(function(click)
    if gui1.Visible then 
        gui1.Visible = false
        gui2.Visible = true
    else
        gui2.Visible = false
        gui1.Visible = true
    end
end)

However, if the button was a parent of either GUI, you would need to add in the script from both buttons and using the same script would work, but changes would be needed.