Hello,
I have achieved at least a partial success on this topic which I would like to share here.
Local language files are controlled by SystemD with the help of localectl.
My system settings are all German and only one admin account is available. Before I create a new account in e.g. English language I have changed one thing.
localectl to control the settings
localectl list-locales | less Display the language files and can be quite with Key "Q„
sudo localectl set-locale de_DE.UTF-8,en_GB.UTF-8 Set the languages separated by a commad
localectl -h Help
man localectl man page
After I made this change I could create an account in english language. Unfortunately some graphical displays are still available in German. Maybe I made a mistake somewhere or did not keep the order.
But I hope that this is helpful for the further procedure.