No. You do not need such a thing for the festival itself.
According to the Youth Protection Act, minors under the age of 16 are not allowed to attend the evening event. Youths over 16 but under 18 are only allowed to attend the evening event if accompanied by a parent (with a completed "Muttizettel"). You can download the form here and have it filled out and signed by your parents: Educationassignment.pdf
This parental consent form does not apply to registration for competitions. For this, your parents must fill out and sign the respective consent forms.