Changing H4 Tags from Footer and Widgets into Paragraph Text

I've trying to change the H4 tags from my Footer and Widgets on the WordPress site https://www.thebitesizedbackpacker.com/ into paragraph text, using functions.php.

I tried several codes (implemented through Code Snippets), but no success so far. I came up with the following base code, but with my limited PHP-knowlegde I could use some help in making this work.

Hope someone can help!

CODE:

add_filter( 'generate_start_widget_title', 'widget_title_start_tag' );
function widget_title_start_tag()
{ 
    return '<span class="widget-title">';
}

add_filter( 'generate_end_widget_title', 'widget_title_end_tag' );
function widget_title_end_tag()
{ 
    return '</span>';
}