How make a complete gui softwaree in a single windows in tkinter

To update without changing the window, you basically have to use the after method, if you use it the correct way, then it will be able update automatically. Here is an example:

def someKindOfFunction():
    #something happening there
    window.after(100,someKindOfFunction)
someKindOfFunction()

This way you will create a loop, you would then have to specify conditions for when you are on the login and where you are not.