Now I have been using the plugin for a few weeks now and successfully imported approximately 300 quizzes into Learndash without a problem. First, I had an issue with the plugin, which later turned out to be a specific setting on my server or so, but support helped me out immediately and solved the issue in a professional manner. The experience is good working with it, import is done fast. Ever since the first issue was fixed, it just does the job. It saves me an awful lot of time.