Connect your watch to Wi-Fi and it will be able to perform its own search and get bookmarks from the phone via iCloud.
You can change the current language directly on the following screens: Terms (text input and results screens) and NearBy, if you firmly press the watch screen.
If your watch is not connected to Wi-Fi, you will have to keep it near your phone to be able to use bookmarks on the device.
The number of articles in different languages varies so the search is carried out with the language taken into account.
Create them beforehand if no Internet connection is expected while you are viewing the articles on your watch or your phone.