Hi

If you open the Firefox for Android menu and select Settings, then General, followed by Language you will either be able to set the language as the same as your Android Device ("system default") or a different language from the list provided.

I hope this helps.

Hi again I do not want to change the language. I prefer the language is fix in English. In setup I always select ( English ) no ( system default ). but almost Firefox will change the language by itself to persian when visit some persian websites so I forced to return it to English manually.

I have the same problem and i temporally stopped using firefox because its annoying. Though i have selected English in option language setting and its showing that the default is English but whenever i open the firefox in my laptop it opens in Arabic.