How can I link already translated pages?

You can link a page that is a translation of another page using the Connect with translations feature.

Here are the detailed steps:

1. Open the translated version of a page for editing.
2. In the right sidebar, expand the Language tab and select to translate the document with the WordPress Editor. Set the correct language of the page. Click OK in the dialog pop-up that appears. The page will reload.

3. Click on Connect with translations in the Language box.

4. Search for the page you want to link, then select it and click Ok.
5. Another dialog appears. If you want to change the page’s original language, select Make [Language] the original language for this page.
6. Click the Assign button.