Changing h3 html tags in enfold child

i guess you can follow this answer here:
https://kriesi.at/support/topic/change-h3-tags-in-footer-widget-child-theme-of-enfold/#post-727939 and from Yigit here:
https://kriesi.at/support/topic/change-h3-tags-in-footer-widget-child-theme-of-enfold/#post-728320

On register-widget-area.php you find the names and ID’s of the widget areas. I cannot see a Forum Widget Area – but you will know that on your installation. ( i let it on section instead of your div – then all would be the same syntax – if you like change section to div)
The normal blog widget is called: Sidebar Blog with id: av_blog
for child-theme functions.php:

function ava_remove_some_widgets(){
	unregister_sidebar( 'av_forum' );

	register_sidebar(array(
		'name' => 'Forum',
		'before_widget' => '<section id="%1$s" class="widget clearfix %2$s">',
		'after_widget' => '<span class="seperator extralight-border"></span></section>',
		'before_title' => '<h4 class="widgettitle">',
		'after_title' => '</h4>',
		'id'=>'av_forum'
	));
}
add_action( 'widgets_init', 'ava_remove_some_widgets', 11 );

For the font size change, couldn’t find the relevant CSS selectors either.

For advice, I would have to see the page it concerns.

_____________________
Off Topic
as long as the headings should be all the same tag i would take this code instead of Yigits – a little bit shorter:
for child-theme functions.php:

function register_custom_footer_widget(){   
    $footer_columns = avia_get_option( 'footer_columns', '5' );
    for ($i = 1; $i <= $footer_columns; $i++){
    unregister_sidebar( 'av_footer_'.$i );

    register_sidebar(array(
      'name' => 'Footer - column'.$i,
      'before_widget' => '<section id="%1$s" class="widget clearfix %2$s">', 
      'after_widget' => '<span class="seperator extralight-border"></span></section>', 
      'before_title' => '<h5 class="widgettitle">', 
      'after_title' => '</h5>', 
      'id'=>'av_footer_'.$i
    ));
  } 
}
add_action( 'widgets_init', 'register_custom_footer_widget', 11 );

hi Yigit – You can’t joke around here anymore either. I was just surprised to be called “Sir”.

Btw.: this code above changes all widget titles to h4 even the footer ones?
i thought he would only change these specific heading tags.