When conducting multiple languages in Lighthouse Studio, most people create the questionnaire and finalize it in one language. Then, they use the "File + Save As" to save a copy of the project as a new project. Then, there's an option for exporting all the phrases used to either .CSV or Xliff file. You then translate the phrases in the .CSV or the .Xliff file to the target language, and then import those into the new Lighthouse Studio project. This is described in the documentation.