Whenever you login via SSH, your locale (the one on the machine your are connecting from) is sent to the server. I assume, you have
de_DE.UTF-8 set locally. Whenever you execute the code snippet from Hetzner while you are logged in on the machine you temporarily switch to a different LC and everything works (for a while).
First off look in
/etc/default/locale. You should find a
LANG="en_US.UTF-8" in there (if not, add it).
I would recommend to install your locale on the server. Try choosing any
de_DE.* in the
dpkg-reconfigure locales dialog..
Or you could append the
export commands (not the other commands!) into your
~/.bashrc on the server, so they will be set automatically whenever you login.
Or you could disable accepting
LANG variables on you SSH server (and your server should fallback to it's default). Therefore remove them from - or uncomment the whole -