I have just thought of an easier option for you, particularly if you are an English speaker
If you got to ‘advanced search’ in opensubtitles.org you will have the option to check the box at the bottom right (picture of a globe) which will select translations of ‘foreign parts only’
When you select a subtitle with the globe symbol, it will only give you subtitles for the 'foreign language' parts of dialogue
These mostly apply to films with English soundtracks where there is some non English dialogue (or French with non French dialogue, etc)
Avatar is one of the exceptions where the language is invented. Here you will get some subtitles other than English where you will get subtitles in your language for the alien bits but the English soundtrack is not translated.
I hope this helps