Hi, Louise,
My first instinct was that this must be part of global settings. I see there is an option to add "available languages" but when I try to add a language, nothing happens.
Not quite correct.
You selected the "base" language when you created the survey.
Additional languages you select here "General settings" of the survey.
Where are these texts and how do I translate them?
System texts like the "mandatory" message are taken from the chosen language depending on the selected language of the survey.
1. German
2. English
If you want to change these system texts you have to edit the language file.
Your questions, subquestions and answer option (everything you entered and are able to change), you may translate either by the "quick translation tool"
or editing each question
Joffm