By the way, I went to the police, looked at windows/locks installed there, broke open a normal window once, and was able to pick up one or two useful pieces of information. Overall, I already had a good overview of most things. It didn’t hurt anyway, after all, it only cost a few euros for fuel.
What came out of it:
- make sure to get a certificate for the professional installation according to the manufacturer’s specifications
- make sure that the window as a whole is RC2-certified and that you are not sold any fake packages (allegedly, mushroom heads are often combined with normal locks or formulations such as "lock is similar to RC2 in terms of security" appear - here you just have to be able to read to get suspicious)
- no lockable handles with buttons without keys
- scrutinize the window (stickers with certificates and information on who tested what and when)