The additional language subtitles you see in the background of videos are hardsubs, i.e., they are burned into the video itself, provided by our content provider, and cannot be turned off.
Subtitles on videos with hardsubs will always have a background to enable easy reading.
However, if you come across any that don't, you can add a background color/opacity to the subtitles added to this show (on top of the hardsubs) by managing your subtitles appearance settings. Learn how you can do so here.
You can turn off subtitles' background color/opacity for other shows when you no longer need them.