Xaver
You can enforce your language selection by an ‘excludes’ file in /etc/dpkg/dpkg.cfg.d – example:
/etc/dpkg/dpkg.cfg.d/excludes
# Drop locales except English and German
path-exclude=/usr/share/locale/*
path-include=/usr/share/locale/en/*
path-include=/usr/share/locale/de/*
path-include=/usr/share/locale/locale.alias
#
# Drop translated manpages except English and German
path-exclude=/usr/share/man/*
path-include=/usr/share/man/man[1-9]/*
path-include=/usr/share/man/en*/*
path-include=/usr/share/man/de*/*Maybe then delete the unwanted locales in /usr/share/locale.