Student needs help with bachelor thesis

Paul Westhoff is looking for test subjects for an online study (30-40 minutes) as part of his bachelor thesis at the University of Lüneburg.
The aim is to solve and evaluate brain teasers.
For their effort, the participants will receive feedback on their performance, also in comparison to the other participants, if desired, and take part in a raffle for Amazon vouchers (3 vouchers of €20 each)
Link to the survey:
http://www.unipark.de/uc/OnlineAssessment/b7f9/
Many thanks
Paul Westhoff
(Supervised by: Prof. Dr. Alexander Freund - Institute of Psychology)