Anaconda Navigator and Spyder don't start

I am having a problem opening Spyder or Anaconda Navigator. Anaconda shell still works without a problem.

I already tried:

1. reinstalling Spyder
2. reinstalling Anaconda
3. opening it from shell with the following result:

(base) C:\Users\***>anaconda-navigator
Traceback (most recent call last):
  File "C:\Users\***\anaconda3\lib\site-packages\qtpy\__init__.py", line 204, in <module>
    from PySide import __version__ as PYSIDE_VERSION  # analysis:ignore
ModuleNotFoundError: No module named 'PySide'
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
  File "C:\Users\***\anaconda3\Scripts\anaconda-navigator-script.py", line 6, in <module>
    from anaconda_navigator.app.main import main
  File "C:\Users\***\anaconda3\lib\site-packages\anaconda_navigator\app\main.py", line 22, in <module>
    from anaconda_navigator.utils.conda import is_conda_available
  File "C:\Users\***\anaconda3\lib\site-packages\anaconda_navigator\utils\__init__.py", line 15, in <module>
    from qtpy.QtGui import QIcon
  File "C:\Users\***\anaconda3\lib\site-packages\qtpy\__init__.py", line 210, in <module>
    raise PythonQtError('No Qt bindings could be found')
qtpy.PythonQtError: No Qt bindings could be found

PyQt5 should be installed (I tryed reinstalling and updating)

I also tried to update conda anaconda and python.

Do you have any suggestions? I already googled a lot, but wasn't able to find anything that works for me.

Thanks in advance!

UPDATE:

Creating a new env with python 3.8.2 allows me to open spyder, but the window stays a white Window and does not respond any more. The following ERROR appears in the shell:

(newEnv) C:\Users\***>spyder
[2280:2332:0331/162242.873:ERROR:broker_win.cc(59)] Error reading broker pipe: Die Pipe wurde beendet. (0x6D)
[4620:17776:0331/162242.873:ERROR:broker_win.cc(59)] Error reading broker pipe: Die Pipe wurde beendet. (0x6D)

Translation: "Die Pipe wurde beendet." - "The pipe was stoped."

Downgrading Python to python 3.7.0 (The last version I know of that it worked) results in the same ERROR from the beginning.