Ok, thanks to this I've found it out:
https://www.anleitung24.com/seblod-anleitung-anzahl-der-eintraege-im-frontend-pro-seite-aendern-individuelles-limit.html
Just add "limit=15" (or the number you like) to the url. In list configuration "pagination" must not be set to "all elements".
By adding a field as mentioned on the first linked page the url parameter "limit=..." appears.