There should be upper right corner a option to set the language did you try that yet. But if you go to a German site that is in German it won't change for english unless the site has a translate version with it. Otherwise you will have to use Chrome that does language conversion on the fly to read in German to English.

Use Firefox in another language https://support.mozilla.org/en-US/kb/use-firefox-another-language

Is the language changing in the browser interface, on web pages or both? Look at Settings > General > Language.

Up to now I have not brought up this problem because the regulations have been usually simple. But since the beginning of the year I keep getting updated Regulations from different Companies whose services that I have been using. These new regulations are now two or three pages long. And one of the biggest Companies who ignores my wishes is MS! Win 10 is installed in English on my PC and in 'Settings' I have placed in the 'Windows display language' window "English (United States)". But there is one service of theirs that I tried using which always opens in German. And another Co. that I have the same problem with is Adobe. I wrote and asked them to send 'all' communications to me in English, and they said that they would. But the last time I looked, I was still receiving mail from them in German. And Mozilla has been doing this to me also. I suspect that it's because they are using my e-mail address as a means of choosing what language to communicate with me in. So would you please stop trying to be so darn helpful ! ! !

If the Firefox user interface (toolbars) is in the wrong language or if you want to change the current language then download Firefox in the language of your choice.

• https://www.mozilla.org/en-US/firefox/all/#product-desktop-release

The language setting in Settings is about the language for the user interface and the preferred language for webpages.

• Settings -> General -> Language and Appearance
• https://support.mozilla.org/en-US/kb/use-firefox-another-language
• https://support.mozilla.org/en-US/kb/choose-display-languages-multilingual-web-pages

Note that some websites check your current location via a reverse DNS lookup and automatically present you pages in the local language. You can possibly use a VPN service with an exit node based in the US to make websites show you page for en-US, this would also work for pages that do not have a language selector.

Beyond the languages Firefox Browser shows what companies send to you in different languages isn't Mozilla or the forum can change. That is up to the company that you request the change from. Regulations are the norm here whether one reads from beginning to end is up to the user of those services. Email address doesn't change language communications. It's based on your what your browser or IP address tells them the language your system Browser is using and they site responds either the change or the language it uses. Your IP or VPN if your using one determines from their side what their sites displays or only displays their Native language. So as before if your having issue you should use Chrome as that Browser can do On-Fly Language changes for one to read. But as of now your asking Mozilla/Firefox to do something they have no control over-firefox isn't like Chrome that can switch languages. Firefox is one language install only and you can as my link above posted you can change your Browser to english but if the site is mostly German it's not going to change to english because you clicked that option. Also if your in Germany the IP address is German so one would expect their side would think your computer is German language by common sense.