Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
To change the language of the Office user interface, you may have to install a language accessory pack. Go to https://support.microsoft.com/en-us/office/language-accessory-pack-for-office-82ee1236-0f9a-45ee-9c72-05b026ee809f.
Installed language packs will display in the Apps & Feature category in Windows Settings. There will be one entry per language, and installing additional languages will start an Office install procedure, very similar to when you first installed Office on the computer. The difference is that the installation of a second language will be faster.