In order to "group" the same website content pages for different languages, you should use the 'group' field on the website content settings.
Use the same group name for all the content pages records of all languages to have the website show the same page when a user will make a change of the display language.
If a user will make a change in the display language and the system will not find a relevant page in the same group, the user will be redirected to the website's homepage.
The "Contact Us" page is displayed in English:
When a user will change the language to Spanish, he will be redirected to the Spanish version of the Contact us page instead of the website homepage.