yeah you are right there was no menu. but now i added some pages. Still the same result.
Below is my code.
<nav class="navbar navbar-default">
<div class="container-fluid">
<div class="row nav-row">
<!-- Brand and toggle get grouped for better mobile display -->
<header>
<div class="navbar-header">
<button type="button" class="navbar-toggle collapsed" data-toggle="collapse" data-target="#navbar-collapse-1" aria-expanded="false">
<span class="sr-only">Toggle navigation</span>
<span class="icon-bar"></span>
<span class="icon-bar"></span>
<span class="icon-bar"></span>
</button>
<a class="navbar-brand" href="<?php echo home_url(); ?>">
<img alt="Brand" src="<?php bloginfo('template_url'); ?>/howtotalks.png">
</a>
</div>
</header>
<!-- Collect the nav links, forms, and other content for toggling -->
<div class="collapse navbar-collapse" id="navbar-collapse-1">
<?php
$args = array(
'theme_location' => 'primary',
'depth' => 2,
'container' => '',
'menu_class' => 'nav navbar-nav navbar-right',
'walker' => new wp_bootstrap_navwalker()
);
?>
<?php wp_nav_menu($args); ?>
</div><!--navbar-collapse -->
</div>
</div><!-- container -->
</nav>