1. You can define an end URL at Limesurvey which can be loaded automatically at the end of the survey. See survey settings -> end URL
2. When using conditions, then this is hard.
Only solution I can think of is showing X of Y questions randomly and then trigger how many questions are answered an setting a condition to all questions to not show anymore once 15 questions were marked as answered.
But that is quite tricky.
Best regards/Beste Grüße,
Dr. Marcel Minke
(Limesurvey Head of Support) Need Help? We offer
professional Limesurvey support Contact: marcel.minke(at)survey-consulting.com'"