Submit comment

Hello Carlager,
To change ‘the submit comment’ to ‘indsende kommentar, just add the below codes in ‘functions.php’ of child theme.

add_filter( 'gettext', 'theme_change_comment_field_names', 20, 3 );
function theme_change_comment_field_names( $translated_text, $text, $domain ) {
    if ( is_singular() ) {
        switch ( $translated_text ) {
            case 'the submit comment' :

                $translated_text = __( 'indsende kommentar', 'your-text -domain' );
               break;
        }
    }
    return $translated_text;
}

It is recommended to create child theme if you are going for the coding option.
https://codex.ww.wp.xz.cn/Child_Themes#How_to_Create_a_Child_Theme