Problem
You changed the Culture dropdown to a different language, but the post text still appears in the old language.
Possible cause
Changing the Culture dropdown only sets the language tag for this version of the article. It does not automatically translate the content. You need to write the text in the selected language yourself.
Solution
Go to the edit screen for the post.
Set the Culture dropdown to the desired language.
Manually edit the title, teaser, and body text to the selected language.
Save the post.
If your system uses separate translations, make sure a translation for the new culture also exists.
If the problem persists, contact support and include details about:
Which languages are involved.
What you expected to see instead.
When the issue occurred.