Hey Detlef1a,
Perhaps you can try Randall suggested that method it should work.
You also can take a quick look at our documentation how to translate those language.
https://stackideas.com/docs/easysocial/administrators/languages/creating-language-overrides
This following is language constant which use to translated those language translation
COM_EASYSOCIAL_WELCOME_TO_YOUR_SOCIAL_SITE="Welcome To Your Social Network"
COM_EASYSOCIAL_WELCOME_TO_YOUR_SOCIAL_SITE_INFO="Collaborate, connect and share moments with your friends and co-workers"
Hope this will help.
By the way, Thanks for sharing Randall