elpy on Windows: No module named 'encodings'

[c.buhtz@posteo.jp]

Hello, I try to get elpy run on Windows.
On Debian 10 I run such an elpy environment. So I know what to expect.

When editing a py-file I got the elpy-output-error
"Fatal Python error: initfsencoding: unable to load the file system 
codec
ModuleNotFoundError: No module named 'encodings'"

Ok, I checked (elpy-config)

Emacs.............: 27.1
Elpy..............: Not found (Python), 1.34.0 (Emacs Lisp)
Virtualenv........: None
Interactive Python: python . 
(c:/Users/Buhtzy/AppData/Local/Microsoft/WindowsApps/python.exe)
RPC virtualenv....: rpc-venv 
(c:/Users/Buhtzy/AppData/Roaming/.emacs.d/elpy/rpc-venv)
  Python...........: c:/WINDOWS/py.exe nil (c:/WINDOWS/py.exe)
  Jedi.............: Not found
  Rope.............: Not found
  Autopep8.........: Not found
  Yapf.............: Not found
  Black............: Not found
Syntax checker....: flake8.exe (c:/Program Files 
(x86)/Python37-32/Scripts/flake8.exe)

Ok, this does not looks good.

When I do "py" on a "Windows Terminal" or on a classic "Command Prompt" 
a Python 3.9.0 prompt comes up. So it is there.
Python2 is not installed - but should not be relevant.

Based on the Windows-Feature list, only Python3.9 is installed - no 
other Python version.

Python3.9 is installed in 
"C:\Users\Buhtzy\AppData\Local\Programs\Python\Python39"

But this two folders still exists:
"c:/Program Files (x86)/Python37-32"
"c:/Program Files (x86)/Python36-32"
But they have no python binaries but a Lib and Scripts sub-folder.

It confuses me. Maye it confuses elpy, too? ;)

What can I do next?