How can I set English as a default language in Debian ? I've installed Debian in a different language.
$ sudo update-locale LANG=en_US.UTF-8 LANGUAGE=en_US update-locale: Error: invalid locale settings: LANGUAGE=en_US LANG=en_US.UTF-8
sudo dpkg-reconfigure locales should work.
Can you start with the output of
env | grep LANG? Make sure those all point to the proper lang/country, then do the dpkg command as mentioned by @vlp
check the language environment variable, that is LC_LANG. An easier way is to set the LC_ALL or LC_* variable to the English utf8.