Does wordpress add their own classes into nav menus?

@user1632018 reports that the problem has been solved:

I removed both the <ul> and <li> tags and now the navigation is in its
proper location:

<div class="header">
    <div class="nav">
       <?php wp_nav_menu( array( 'theme_location' => 'primary' ) ); ?>

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)