Application doesn't start due to Numpy Import Error: "No module named 'numpy.core._multiarray_umath'"

OS: Win 10
PsychoPy version: 2022.1.3
Standard Standalone? y
What are you trying to achieve?: Start The Application

What did you try to make it work?: Reinstalling numpy and setuptools, Reinstalling PsychoPy, Starting the Application via CMD

What specifically went wrong when you tried that?:
Eventhough PsychoPy has worked fine for two years, it stopped starting now.
When starting it via python.exe -m psychopy.app.psychopyApp in the console, following error occurs:

    from numpy.core._multiarray_umath import (
ModuleNotFoundError: No module named 'numpy.core._multiarray_umath'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "C:\Users\sebif\AppData\Local\Programs\Python\Python39\Lib\site-packages\numpy\__init__.py", line 144, in <module>
    from . import core
  File "C:\Users\sebif\AppData\Local\Programs\Python\Python39\Lib\site-packages\numpy\core\__init__.py", line 49, in <module>
    raise ImportError(msg)
ImportError:

IMPORTANT: PLEASE READ THIS FOR ADVICE ON HOW TO SOLVE THIS ISSUE!

Importing the numpy C-extensions failed. This error can happen for
many reasons, often due to issues with your setup or how NumPy was
installed.

We have compiled some common reasons and troubleshooting tips at:

    https://numpy.org/devdocs/user/troubleshooting-importerror.html

Please note and check the following:

  * The Python version is: Python3.8 from "C:\Users\sebif\AppData\Local\Programs\PsychoPy\python.exe"
  * The NumPy version is: "1.22.0"

and make sure that they are the versions you expect.
Please carefully study the documentation linked above for further help.

Original error was: No module named 'numpy.core._multiarray_umath'

(I hope it was fine, using the code backticks for the error message too)

Further context: PsychoPy stopped working after I’ve tried getting neurokit2 to run in Spyder (installed as a standalone too). For this I reinstalled sklearn.
In all honesty: will it be faster to just reset my machine and install every python stuff anew?

Thank you very much in advance.