I solved my own question without breaking the url structure logic, as Krzysiek Dróżdż (thanks!) suggested.
I changed the page named /page-actueel-blog to the custom-post-type ‘archive’ template. Pretty obvious, but I thought archive was something else entirely.
For whoever may have the same doubts: the archive template is the level up from domain.com/blogpost (single-mycustomposttypename.php); a collection page of all posts. I named it archive-mycustomposttypename.php.