To change the language of hard-coded text appearing on your store pages you can simply alter the Locale of the Store View. However, it won’t help you with the translation of each word on a page. The text includes only:
Besides, you can use the Inline Translation to translate any of the elements, as well as other text content, in case they haven’t been changed.
When running your store on a multi-national basis on different languages you may have a problem with order sequence. To solve it try out our Magento 2 Order Number.
A language pack contains translation files for different text content on your Magento 2 website. E.g.: translation files for standard phrases and email templates, full translations for Community and Enterprise editions.
To download a free or buy a paid language pack you can switch to the official Marketplace. Find a necessary extension under the Content & Customization category and proceed to the next settings.
Install the language pack you have chosen from Component Manager.
composer require company/language-pack-de-de
php bin/magento setup:upgrade
php bin/magento setup:static-content:deploy de_DE