Firefox translates the word "Deutsch" to "English" (probaly other languages too)?

I really appreciate Firefox's built in translator; it is extremely helpful. However there is one thing that bugs me, when translating a page that has multiple language options. For example, when translating a page from German to English, the word "Deutsch" (often listed in the website's built in language settings) is translated not to "German", but to "English". While technically correct in that the page is now displaying English thanks to the Firefox translation, it would probably be better to show "German" so that it is easier to switch the website language and not have a duplicate "English" option in the website's dropdown menu. I have noticed this on multiple websites, specifically with German, but it might be with other languages as well. Hopefully this explanation of the issue makes sense, and see my attached screenshot which shows this issue. Please let me know if there is somewhere else I should submit this too.