Note: Smaller languages (Catalan, Basque) may be only 200–400 MB.
Cause: You are trying to install a 32-bit pack on 64-bit Office, or vice versa.
Usually, the offline process involves downloading a disk image (ISO) or a self-extracting executable containing the language files. Once executed, the installer detects your installed Office 2016 version and seamlessly integrates the new language files into Word, Excel, PowerPoint, and Outlook. Microsoft Office 2016 Language Pack Offline Installer
If you use Office 365 with the 2016 interface, the same Language Accessory Pack rules apply.
Are you using or retail retail copies?
Installing from a local drive or a USB flash drive is significantly faster than streaming files from cloud servers.
Accept the license terms and click "Continue". Installation: The installer will copy files to your system. Finish: Click "Close" once the installation is complete. How to Configure the New Language in Office Note: Smaller languages (Catalan, Basque) may be only
The Help language is separate. Go to File > Options > Language > Help Language and select your preferred language. Reboot.