bimbim what are you trying to do?
Language packs are regular Flarum extensions that provide Yaml-formatted files with translations for specific locales.
English is usually bundled with extensions so each extension will have its own bundled translations.
If you want to customize a text just for your website, I recommend using the Linguist extension https://discuss.flarum.org/d/7026-linguist-customize-translations-with-ease
If you want to correct a typo, contact the extension developer for English or visit the language pack discussion for other languages. Many of the languages are managed through Weblate where anyone can post suggestions to be included in a future update.
