Screen GUI isn't correctly resized , how to position it correctly ?

Hello !

A good friend of mine gave me a ScreenGUI , There is a TextBox and a Button . If something is typed on the TextBox and that we press the button , the text appears for everyone on the screen , I looked into the script I understood it (even if I'm probably the worst at trying to understand scritpts)

function Nameplate()
    local returnedname = game.Workspace.MainScripts.ReturnName:InvokeServer()
    script.Parent.Text = returnedname
    script.Parent.Parent.Visible = true
    script.Parent.Parent.Position = UDim2.new(0,0,0,0),
    script.Parent.Parent:TweenSize(UDim2.new(0,0,0,0), "Out", "Quint", 3, true)
    wait(5)
    script.Parent.Text = ""
    script.Parent.Parent:TweenSize(UDim2.new(0,0,0,0),"InOut","Quad",1)
    wait(1)
    script.Parent.Parent.Visible = false
    script.Parent.Parent.Position = UDim2.new(0,0,0,0)
    script.Parent.Parent.Size = UDim2.new(0,0,0,0)
end

game.Workspace.MainScripts.Nameplate.Changed:connect(Nameplate)

The Problem is that I just don't know how to resize it correctly , I tried but it always messed up . It's supposed to ''open'' at the middle of the left side , expand to the right side and then after 5 seconds close at the left side again . I tried to place some numbers to see how it works but still weird for me (I'm sure as hell it's easy and I'm going to get slapped lol)

Thanks !