‘office’ = a place or a building where matters of business, government department/agency or organisation are discussed, action taken on some activities and problems solved; the entire staff — management and employees — of a business, department or organisation in general

Note: ‘Official’ is more often used as an adjective to refer to something that is done wh the approval of some authority or government, e.g. “The official opening of the new office., i.e. the office is opened by some government dignitary and it has been included in the government records.” & “The official figure of the flood victims is 100., i.e. the number announced by the government is 100, but the TV and newspaper media may have a different figure which is usually higher than the official figure.”