I have had German as my main language about a year ago. Later I changed it to English.
Most parts of the system accepted the change.
The notable exceptions are the package descriptions, which remain in German for some packages.
You can see in the image (apt-cache and software-center), that while some descriptions are in English, some have remained in German. So the question is: how do I reset this? I guess that there is somewhere a description cache that needs to be told that it should update all descriptions?
EDIT: As asked: the output of some language related commands:
$ cat /etc/default/locale
LANG="en_US.UTF-8"
$ apt-config dump | grep Lang
Acquire::Languages "";
Acquire::Languages:: "de_DE";
Acquire::Languages:: "de";
Acquire::Languages:: "en";
Acquire::Languages:: "none";
$ locale
LANG=de_DE.UTF-8
LANGUAGE=en
LC_CTYPE="de_DE.UTF-8"
LC_NUMERIC="de_DE.UTF-8"
LC_TIME="de_DE.UTF-8"
LC_COLLATE="de_DE.UTF-8"
LC_MONETARY="de_DE.UTF-8"
LC_MESSAGES="de_DE.UTF-8"
LC_PAPER="de_DE.UTF-8"
LC_NAME="de_DE.UTF-8"
LC_ADDRESS="de_DE.UTF-8"
LC_TELEPHONE="de_DE.UTF-8"
LC_MEASUREMENT="de_DE.UTF-8"
LC_IDENTIFICATION="de_DE.UTF-8"
LC_ALL=
As a note: I'm not sure what each entry means, but some of the de_DE.UTF-8 are probably ok, since I do want paper-sizes, monetary, time, etc. in standard German formats.
