hide eventregistration in event detail

Also I set the registration to no and still see the Registration Form in the frontend. Why?

In the code there is this if-condition where the registration begins:
<?php if ($this->showAttendees && $params->get('event_show_registration', '1')) : ?>

but in the event I cannot turn off the display of attendees and I somehow this if does not work and shows the form despite registration is set to no

This button is in the general JEM setting.

cache cleaned, before testing?
Do you use general JEM setting oder menue event setting?

yes, cache is cleaned. I use the general setting, no menu item

I can't reproduce your issue: when my settings are like in image, I don't see event registration, even when eventregistration is on.