Hi @Şafak Yacan,
I suggest you sign in to this web:
https://myaccount.microsoft.com/?ref=OfficePortalSecurityPrivacy
Go to sign in Microsoft 365 portal and check if you can find the Microsoft Office product under the Subscriptions tab:
If you cannot find the Office license, try to contact your university's Administrator.
If the Office product is still existed, please refer to this support article about how to uninstall Office from Mac completely:
Then you can re-install the Office for Mac and sign in your account to check the result.
Just checking in to see if the information was helpful. Please let us know if you would like further assistance.
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