Hey there, I'm assuming you're referring to Firefox built in translation feature. When you visit a page in a language not added to the exclusion list, it will offer to translate for you.

You can disable this popup for a language by clicking the cog wheel (circled in red) and simply uncheck "always offer to translate" to remove this popup for all sites of this language.

You can learn more about the translation feature at the appropriate [support page]. Hope this answered your question :)

I thank you for the suggestion but my question was how to block or delete this untimely translation feature on firefox

To block the translation feature, click the cog icon and uncheck "always offer to translate". It's for all languages.

Thank for try to help me but is no "check or uncheck" offer to translate !