Hello, thank you for reaching out to Microsoft Q&A.
First step,
Enable Account Security Measures by following the steps here:
1. Reset your Microsoft account password.
Open an InPrivate/Incognito browser window and use the following link to reset your password: https://account.live.com/ResetPassword.aspx
2. Sign out of your account from all sessions.
Once the password reset is successful, sign in with your account here: https://account.live.com/proofs/Manage
Scroll down until you find Sign out everywhere. Select Sign out everywhere. Your account will be signed out of all the trusted devices, possibly within 24 hours.
3. Enable two-step verification.
On the Security settings page, under Additional security, turn on Two-step verification. Make sure you have at least 3 active security verification methods.
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Next, change the Outlook App language from your Microsoft account user profile and from the App settings.
Open any web browser and sign in with your Microsoft account here-
https://account.microsoft.com/profile
- Change the Language and region format in your Microsoft profile if it is set to something different.
Then open the Outlook desktop app or Outlook on the web to read your email.
Go to Settings > Time & Language, change the language there, and then restart Outlook.
If you are using Outlook Web, copy and paste the link below to change the language settings.
https://outlook.live.com/mail/0/options/general/timeAndLanguage
Let me know if you still need more help.