As I expected, it originates from the BildZeitung! 🤣
https://www.bild.de/politik/inland/staatsschuetzer-schlaegt-alarm-deutsche-kinder-konvertieren-aus-angst-zum-islam-66264176841ad84a3ea833d8?ticket=ST-A-34005-aWLqrudJ1ATAG5bZwXue-sso-signin-server
The Daily Mail (which is the source of the OP) added an extra level of distortion and confusion, as it tends to presents statements by an anonymous "Staatschutzer" in a way they can be confused with findings of the study. the Daily Mail also doesn't highlights that it was a survey among Muslim students.
Gosh, the Daily Mail has even less professional ethics that the Bildzeitung. 😆
Oh and It's also written in the BZ that the sample is not representative.