Hey Movin,
thank you for your answer.
Unfortunately it is not. 
Can it may be that I have to put in the following code into the functions.php?:
$query = new WP_Query( array( ‘cat’ => $slidecat, ‘posts_per_page’ => $count, ‘post_type’ => ‘page’, ‘slider_page’ => ‘yes’ ) );
In this thread you wrote that I have to make a custom field, therefore my question: https://colorlibsupport.com/t/slider-for-pages/