Regarding Page Content in Multi language

Hello,

i installed Elegant Nova Theme link of theme is below
https://www.elegantthemes.com/preview/Nova/

and i installed Multilanguage by BestWebSoft pluign for language change i checked i am able to change title and description in differenct language but in that post or page having Custom Field Thumbnail i want to put different Thumbnail in both Spanish and English Language but when i paste different Image url in that Custom Field Thumbnail and when i save then both place same url of image why i am not able to save different custom field Thumnail for both language?

Thanks

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