Modify post filter to set custom number of posts per page and exclude child posts

Just call $query->set 2 times:

$query->set('posts_per_page', 48 );
$query->set('post_parent', 0 );

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)