Windows 8.1 Pro x64 None of the Modern UI apps work, Powershell, CMD, and wsreset returns error

So, today somehow my pc got messed up while I wasn't home, don't ask how because i don't know (maybe a windows update gone wrong, or ghosts were messing with it :) ) First it started with black scrn after login that I fixed it by refreshing Windows from an install media. Than I got my desktop back but all modern ui apps got messed up not even the PC Settings will start. So I looked up the problem on the internet but all of the fixes fail.

wsreset.exe quits with an error message what I can't translate to English because it doesn't makes any sense in my native language :( (poor windows translation)

Than the Powershell -ExecutionPolicy Unrestricted Add-AppxPackage -DisableDevelopmentMode -Register $Env:SystemRoot\WinStore\AppxManifest.xml command fails with this error:

C:\WINDOWS\system32>Powershell -ExecutionPolicy Unrestricted Add-AppxPackage -Di
sableDevelopmentMode -Register $Env:SystemRoot\WinStore\AppxManifest.xml
Add-AppxPackage : Deployment failed with HRESULT: 0x80073CF6, The package can't be registered.
An internal error occurred with error 0x80073D05. See http://go.microsoft.com/f
wlink/?LinkId=235160 for help diagnosing app deployment issues.
NOTE: For additional information, look for [ActivityId] 1f01eb1f-b06a-0002-6ded
-011f6ab0d001 in the Event Log or use the command line Get-AppxLog -ActivityID
1f01eb1f-b06a-0002-6ded-011f6ab0d001
At line:1 char:1
+ Add-AppxPackage -DisableDevelopmentMode -Register $Env:SystemRoot\WinStore\Ap
pxM ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~~~
    + CategoryInfo          : WriteError: (C:\WINDOWS\WinStore\AppxManifest.xm
   l:String) [Add-AppxPackage], IOException
    + FullyQualifiedErrorId : DeploymentError,Microsoft.Windows.Appx.PackageMa
   nager.Commands.AddAppxPackageCommand


C:\WINDOWS\system32>

This ((Get-ChildItem "HKLM:SOFTWARE\Microsoft\Windows\CurrentVersion\Appx\AppxAllUserStore\InboxApplications") | Get-ItemProperty).Path | Add-AppxPackage -Register -DisableDevelopmentMode Powershell command fails with this error:

Add-AppxPackage : Deployment failed with HRESULT: 0x80073CF6, The package can't be registered.
An internal error occurred with error 0x80073D05. See http://go.microsoft.com/fwlink/?LinkId=235160 for help diagnosing
 app deployment issues.
NOTE: For additional information, look for [ActivityId] 1f01eb1f-b06a-0000-0cee-011f6ab0d001 in the Event Log or use th
e command line Get-AppxLog -ActivityID 1f01eb1f-b06a-0000-0cee-011f6ab0d001
At line:1 char:134
+ ... operty).Path | Add-AppxPackage -Register -DisableDevelopmentMode
+                    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : WriteError: (C:\Windows\vpnp...ppxManifest.xml:String) [Add-AppxPackage], IOException
    + FullyQualifiedErrorId : DeploymentError,Microsoft.Windows.Appx.PackageManager.Commands.AddAppxPackageCommand

The most annoying thing is, that I can't create a new local user to check out if the problem is global or user related because you need the modern ui settings app for that.

I checked the folder/file/registry permissions and all seems to be in order, but the error message couldn't be more specific than this "WriteError"

Now I'm stuck. I have no clue what to do next. What I know is that I don't want to do a clean Windows install.

Is there anything I can try to fix this problem?

This script fix registry premissions for appx installer and can help https://gallery.technet.microsoft.com/scriptcenter/Re-registers-Modern-Appx-2e528428#content

Description from page:

Re-registers Modern Appx packages that won't launch due to registry permissions

This script is designed to fix Modern (Windows 8.x) apps that will not launch and cannot be re-registered due to a permission error with a specific registry key. There are multiple examples of this error on answers.microsoft.com."

Script name: ModernAppRegFix.ps1

It's look like script take keys from

HKCU:Software\Classes\Local Settings\Software\Microsoft\Windows\CurrentVersion\AppModel\SystemAppData\

and reset ownership to user NT AUTHORITY\SYSTEM for subkeys in section with name ending \PSR. After fixing permissions script register applications.