Hi, Frustrated. I'm sorry to hear you're having this problem, and I hope I can assist you to find a satisfactory solution.
I'll give you some checks to do:
Set Finnish as the Default Display Language
Open Settings:
Press Win + I to open the Settings app.
Go to Time & Language:
Navigate to "Time & Language" > "Language."
Add Finnish Language Pack (if not already added):
Click "Add a language" and search for "Finnish."
Select "Suomi" (Finnish) and click "Next."
Ensure "Set as my display language" is checked, then click "Install."
Set Finnish as Default:
If Finnish is already added, click on it and select "Options."
Make sure the "Set as display language" option is enabled.
Check Language for Welcome Screen and New User Accounts
Advanced Settings:
In the same "Language" settings page, on the right pane, click on "Administrative language settings."
Copy Settings:
In the "Region" dialog, go to the "Administrative" tab.
Click "Copy settings."
Ensure the checkboxes for "Welcome screen and system accounts" and "New user accounts" are both checked.
Click "OK."
Remove Other Language Packs
Open Language Settings:
Go back to "Time & Language" > "Language."
Remove Unwanted Language Packs:
Remove any languages other than Finnish.