Last updated post in wordpress homepage first position

To achieve the intended result, you must change the sorting from default by date of publication to the modification date. To do this, you can use the pre_get_posts filter hook, the appropriate value for the orderby query parameter can be found here. To apply changes only on the home page, the conditional tag is_home() will be used.

add_action( 'pre_get_posts', 'se338231_home__sort_by_modified_date' );
function se338231_home__sort_by_modified_date( $query )
{
    if ( !is_home() || !$query->is_main_query() )
        return;

    $query->set( 'orderby', 'modified' );
}