Can't select other Languages than Engllish - United States

Hi everybody,
at the “Configuration”-Page I can’t select another Default language than “English - United states”.
In the Logfiles I can find the following entry:

“mautic.ERROR: An error occurred while attempting to fetch the language list: Failed connect to updates.mautic.org:443; Connection refused”

The Mautic Server is behind a Proxy so I put

ProxyRemote * http://xxx.xxx.xxx.xxx:8080

To my apache config file. I disabled the firewall and SELinux (It’s a redhat Linux). If I run wget as apache user

sudo -H -u apache bash -c ‘wget https://updates.mautic.org

there is no error, but the above mentioned Log-Entry still appears if I want to change the language. Any ideas?

Thank you in advance.

Or, as a workaround, could you please tell me how to manually add the german Translation?

CoreBundle/Helper/LanguageHelper.php

you can find link - just copy/paste in browser

https://updates.mautic.org/index.php?option=com_mauticdownload&task=downloadLanguagePackage&langCode=de