Editing comment form default fields

Hey there!

I have a similar problem like this user.

I want to customize my comment form. First I want to change the comment form title and second I’d like to add label elements to the input fields author and email – I used two filters to achieve this.

add_filter( 'generate_leave_comment','ryb_custom_leave_comment' );
function ryb_custom_leave_comment() {
    return 'Ich freue mich über deinen Kommentar:';
}

and

add_filter( 'comment_form_default_fields', 'ryb_change_comment_form_default_fields' );
function ryb_change_comment_form_default_fields( $fields ) {
    $commenter = wp_get_current_commenter();
    $required = get_option( 'require_name_email' );

    $fields['author'] = sprintf(
        '<label for="author">%1$s</label><input placeholder="%1$s%3$s" id="author" name="author" type="text" value="%2$s" size="30"%4$s />',
        esc_html__( 'Name', 'generatepress' ),
        esc_attr( $commenter['comment_author'] ),
        $required ? ' *' : '',
        $required ? ' required' : ''
    );

    $fields['email'] = sprintf(
        '<label for="email">%1$s</label><input placeholder="%1$s%3$s" id="email" name="email" type="email" value="%2$s" size="30"%4$s />',
        esc_html__( 'Email', 'generatepress' ),
        esc_attr( $commenter['comment_author_email'] ),
        $required ? ' *' : '',
        $required ? ' required' : ''
    );

    return $fields;
}

The first one works and the title has changed as you can see while looking at the site. But the second filter won’t apply regardless of what I’m doing. I already cleared plugin and server cache and even disabled them completely but the changes won’t apply. I just removed the is-screen-reader-class (or something like that) from the label elements so that I can use them as regular labels.

What am I doing wrong? I add PHP via functions.php of my child theme.

Cheers
Philipp