Thank you for your help!
Real is that after which I look. Only I would still want:
from the main window go to Window_1 and than back,
from the main window go to Window_2 and than back,
from the main window go to Window_3 and tahn back.
What is wrong here???

 Code:
setconsole("hide")
$Version = "Version 1.0"
$System = CreateObject("Kixtart.System")


$Form1 = $System.Form()
$Form1.Text = "Window " + $Version
$Form1.BackColor = Green
$Form1.Size = 600,400
$Form1.SysMenu = 0

$Form2Button = $Form1.Controls.button("Button")
$Form2Button.Width = 120
$Form2Button.Height = 50
$Form2Button.Text = "GoTo_Window_1"
$Form2Button.Top = 10
$Form2Button.Left = 10
$Form2Button.OnClick = "SwitchForms('GoTo_Window_1')"

$Form3Button = $Form1.Controls.button("Button")
$Form3Button.Width = 120
$Form3Button.Height = 50
$Form3Button.Text = "GoTo_Window_2"
$Form3Button.Top = 65
$Form3Button.Left = 10
$Form3Button.OnClick = "SwitchForms2('GoTo_Window_2')"

$Form4Button = $Form1.Controls.button("Button")
$Form4Button.Width = 120
$Form4Button.Height = 50
$Form4Button.Text = "GoTo_Window_3"
$Form4Button.Top = 120
$Form4Button.Left = 10
$Form4Button.OnClick = "SwitchForms3('GoTo_Window_3')"

$Form1QuitButton = $Form1.Controls.button("Button")
$Form1QuitButton.Width = 120
$Form1QuitButton.Height = 50
$Form1QuitButton.Text = "Exit"
$Form1QuitButton.Top = 285
$Form1QuitButton.Left = 10
$Form1QuitButton.OnClick = "ExitForms()"

$Form1.Center
$Form1.Show()


CreateForm2()

$Running = 1
While $Running = 1
  $Nul = Execute($Form1.DoEvents())
  $Nul = Execute($Form2.DoEvents())
  Loop
Exit 0

;======================WINDOW_1==========================

Function CreateForm2()
$Form2 = $System.Form()  
$Form2.Text = "GoTo_Window_1 " + $Version
$Form2.BackColor = Green
$Form2.Size = 600, 400
$Form2.SysMenu = 0
  
$Form1Button = $Form2.Controls.button("Button")
$Form1Button.Width = 120
$Form1Button.Height = 50
$Form1Button.Text = "Back"
$Form1Button.Top = 10
$Form1Button.Left = 10
$Form1Button.OnClick = "SwitchForms('Back')"

$Form2QuitButton = $Form2.Controls.button("Button")
$Form2QuitButton.Width = 120
$Form2QuitButton.Height = 50
$Form2QuitButton.Text = "Exit"
$Form2QuitButton.Top = 285 
$Form2QuitButton.Left = 10
$Form2QuitButton.OnClick = "ExitForms()"
  
EndFunction

Function SwitchForms($FormName)
  Select
    Case $FormName = "Back"
      $Form2.Hide
      $Form1.Center
      $Form1.Show()
    Case $FormName = "GoTo_Window_1"
      $Form1.Hide
      $Form2.Center
      $Form2.Show()
   EndSelect
EndFunction


;======================WINDOW_2============================

CreateForm3()

$Running = 1
While $Running = 1
  $Nul = Execute($Form1.DoEvents())
  $Nul = Execute($Form3.DoEvents())
  Loop
Exit 0

Function CreateForm3()
$Form3 = $System.Form()  
$Form3.Text = "GoTo_Window_2 " + $Version
$Form3.BackColor = Green
$Form3.Size = 600, 400
$Form3.SysMenu = 0
  
$Form3QuitButton = $Form3.Controls.button("Button")
$Form3QuitButton.Width = 120
$Form3QuitButton.Height = 50
$Form3QuitButton.Text = "Exit"
$Form3QuitButton.Top = 285 
$Form3QuitButton.Left = 10
$Form3QuitButton.OnClick = "ExitForms()"

EndFunction

Function SwitchForms2($FormName)
  Select
     Case $FormName = "GoTo_Window_2"
      $Form1.Hide
      $Form3.Center
      $Form3.Show()
EndSelect
EndFunction


;======================WINDOW_3============================

CreateForm4()

$Running = 1
While $Running = 1
  $Nul = Execute($Form1.DoEvents())
  $Nul = Execute($Form4.DoEvents())
  Loop
Exit 0

Function CreateForm4()
$Form4 = $System.Form()  
$Form4.Text = "GoTo_Window_3 " + $Version
$Form4.BackColor = Green
$Form4.Size = 600, 400
$Form4.SysMenu = 0
  
$Form4QuitButton = $Form4.Controls.button("Button")
$Form4QuitButton.Width = 120
$Form4QuitButton.Height = 50
$Form4QuitButton.Text = "Exit"
$Form4QuitButton.Top = 285 
$Form4QuitButton.Left = 10
$Form4QuitButton.OnClick = "ExitForms()"

EndFunction

Function SwitchForms3($FormName)
  Select
     Case $FormName = "GoTo_Window_3"
      $Form1.Hide
      $Form4.Center
      $Form4.Show()
EndSelect
EndFunction


Function ExitForms()
  $Running = 0  
EndFunction