Issue on mobile devices

Hi,
I get an issue on mobile devices with my menu and part of my style.
I use a child theme and media queries in my style.css.
I get 2 top menus that I display one below theother on laptop and I would like to gather both with toggler button on mobile devices.
So I have created a third menu ‘navigation mobile” in my admin.
In my header.php I have:

<nav id="site-navigation" class="navigation-main mobile" role="navigation">
<h1 class="menu-toggle"><?php _e( 'Menu', 'expound' ); ?></h1>
			<?php

$defaults = array(
	'theme_location'  => 'mobile',
	'menu'            => 'Navigation mobile',
	'container'       => 'div',
	'container_class' => '',
	'container_id'    => '',
	'menu_class'      => 'menu',
	'menu_id'         => '',
	'echo'            => true,
	'fallback_cb'     => 'wp_page_menu',
	'before'          => '',
	'after'           => '',
	'link_before'     => '',
	'link_after'      => '',
	'items_wrap'      => '<ul id="%1$s" class="%2$s">%3$s</ul>',
	'depth'           => 0,
	'walker'          => ''
);

wp_nav_menu( $defaults );

?>

			<?php do_action( 'expound_navigation_after' ); ?>
		</nav><!-- #site-navigation -->

I use add-on “window resize” on Chrome browser and it displays well when I resize the window (320px or 480px width) except that the toggler button does not appear at the width wanted but at 616px.
I put at @media (max-width: 600px) `.mobile{
display: block !important;
}`
And on mobile devices, I lost a menu and the toggler button does not appear.
Plus, my sidebars don’t take the full width of the screen.

But I repeat with the add-on “window resize”, it looks great.

Please somebody can help me?
Cheers.