Configuring preferences and options in Outlook.com
@Betty Davis said
My outlook language has been changed to a foreign language
If the AI Answer did not help you get your Outlook language back to normal, please advise and I'll offer some other suggestions.
But, a language change that you didn't perform can often be an indication that your account might have been compromised. Please check your Recent Activity Page and advise if there have been any successful sign-ins to your account that you can not account for.
https://support.microsoft.com/en-us/accounts-billing/security/what-is-the-recent-activity-page