the original span must have been deleted through some edits or by the translation.
check the theme’s /inc/template-tags.php file for this section, or check if your child theme’s functions.php has a corresponding code:
if ( ! function_exists( 'twentynineteen_posted_by' ) ) :
/**
* Prints HTML with meta information about theme author.
*/
function twentynineteen_posted_by() {
printf(
/* translators: 1: SVG icon. 2: post author, only visible to screen readers. 3: author link. */
'<span class="byline">%1$s<span class="screen-reader-text">%2$s</span><span class="author vcard"><a class="url fn n" href="%3$s">%4$s</a></span></span>',
twentynineteen_get_icon_svg( 'person', 16 ),
__( 'Posted by', 'twentynineteen' ),
esc_url( get_author_posts_url( get_the_author_meta( 'ID' ) ) ),
esc_html( get_the_author() )
);
}
endif;