It literally translates to "Much luck for [your] birthday".
The German version of "Happy Birthday" is a fascinating blend of international adaptation and deep-rooted local traditions. While the most literal equivalent is "Zum Geburtstag viel Glück," Germans often use their own traditional songs and strict social customs that differ significantly from English-speaking cultures. The Core Song: "Zum Geburtstag viel Glück" happy_birthday_german_version
Watch this video to hear the pronunciation and melody of the standard German version: It literally translates to "Much luck for [your] birthday"