Is this about the language on the Twitch website? Some websites do a reverse DNS lookup of your IP and redirect you, if available, to the local page for your location. Most websites that do this have a language/country selector to bypass this automatic redirect. Such a selection is usually stored in a cookie, so you need to create a cookie allow exception and keep this cookie (clearing the "Site settings" removes all exceptions).

I talk about BROWSER language. HOW to change it on English?

If the Firefox user interface (toolbars) is in the wrong language or if you want to change the current language, download Firefox in the language of your choice. You can find the full installer of the current Firefox release (121.0) in all languages and all operating systems here:

• https://www.mozilla.org/en-US/firefox/all/#product-desktop-release
• https://www.mozilla.org/en-US/firefox/121.0/releasenotes/