Hello @Damir Angel ,
Please see the following Microsoft Support articles.
Retrieve a username or password: https://support.microsoft.com/office/i-forgot-the-username-or-password-for-the-account-i-use-with-office-eba0b4a2-c0ae-472c-99f6-bc63ee2425a8
Share your Microsoft 365 Family subscription: https://support.microsoft.com/office/share-your-microsoft-365-family-subscription-b389b9ce-3ae3-4a82-9017-39d79972fcba
Thank you,
Alison