Fifi.org has most of its pages in both French and English.
If correctly configures, the browser should pick automatically your language of choice:
You need to add either French (fr) or English (en), but not the national variants (Belgian French (fr_BE) or U.S. English (en_US)). You can also have national variants if you wish, but you must also have the non-national variant listed (fr and/or en).
Once you've made the change, you might want to purge your browser's cache so that the new pages are loaded.
If no language has been configured, or if there is no translation for a chosen language, the English pages will be served.