Quick summary of how it works:

It forces Windows to install the full language pack. (Using only Windows Settings installs a simplified version.)
It updates all system elements to the selected language.
After restarting, the language will be fully applied 😊
Here it is—just copy everything below and paste it into PowerShell:

# --- Variables ---
$targetLanguage = "en-US" # Replace with the desired language code (e.g., "en-US", "fr-FR")
# --- Install Language Pack ---
# Ensure you have the necessary language pack on your system or a local repository
# You can use Add-WindowsCapability -Online -Name "Language.es-ES~..." for feature-on-demand languages or install the pack from a local ISO [5, 11]
# Example using Install-Language cmdlet:
Install-Language -Language $targetLanguage
# --- Set User Display Language ---
# This sets the language for the current user
Set-WinUserLanguageList $targetLanguage -Force
# --- Copy Settings to System and Welcome Screen ---
# This applies the language to the system and the welcome screen
# You may need to run this section in a separate user session for it to fully apply
# Or use a scheduled task to run it under the logged-on user [7, 9]
Copy-UserInternationalSettingsToSystem -WelcomeScreen $True
# --- Force a Restart to Apply Changes ---
# A reboot is required for the changes to take effect system-wide [1, 9]
Restart-Computer -Force

Now, if it works for you or if you still have the problem, please let me know!