styling sidebar widgets to look like other sidebar features

correction, the current code I have in the sidebar file is here: https://pastebin.com/HArFKwC7

I want to get my widgets (depicted as “Text Widget Test 1” and “Text Widget Test 2”) to each be styled just like the ADVERTISING and FOLLOW OUR UPDATES sidebar sections where they’re styled like this:

top (down-curved background)
content (w/rectangle background)
bottom (up-curved background)

please advise how i edit the php in the “sideb” div at the top of my sidebar.php file to get it to look like this, and match the other sidebar items????

and i dont know if it helps, or is related, but there’s a section of code in my functions.php file that i think is related:

if ( function_exists('register_sidebar') )
    register_sidebar(array(
        'before_widget' => '<li class="widget">',
        'after_widget' => '</li>',
        'before_title' => '<h2 class="widget">',
        'after_title' => '</h2>',
));
?>

to make a long story short, i’m still learning the intricacies of php and dont know how to style this. please advise. thanks!

i got it figured out. i toyed with it and now it looks like this and works.

if ( function_exists('register_sidebar') )
    register_sidebar(array(
        'before_widget' => '<li class="widget">',
        'after_widget' => '<div class="sidebar-bottom-widget"></div></li>',
        'before_title' => '<h2 class="widget">',
        'after_title' => '</h2>',
));