In order to translate the Magento CMS Page follow the steps:
1. Navigate to Content > Elements > Pages. Note that the translation of the page requires manual creation of a new one so decide which page you want to translate.
2. Press the Add New Page to start.
3. Enable the page and set its Title.
4. Enter the Heading of the Content and Content.
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5. Set the URL Key in the Serch Engine Optimization field in order to let the search engine know the route to the Magento CMS page.
6. Choose which store view to post the new CMS page on in the Page in Websites section.
Once you've filled in all the necessary information don't forget to press the Save Page button and go to the storefront to check out the newly created Magento 2 CMS page.
After you've successfully translated the Magento 2 CMS page you may be directed to the 404 Page while trying to switch one storefront to another.
That usually happens because of the absence of the alternate hreflang tags on each of those pages to direct the readers to the other. In case you want two or more Magento 2 CMS pages in different languages to be interconnected you can install the Magento 2 Alternate Hreflang extension.
CMS Page Translation is just one of the series of articles about How to Configure Multi-Language Magento Website? which include information about the creation of a new store view, language packs installation, useful multi-language store extensions, product&category, email templates, and other translations in the Magento 2 website. You should definitely get acquainted with them in order to know how to manage a multilanguage store.