Show Logged in user to Nav menu

 //Add login/logout link to naviagation menu
function add_login_out_item_to_menu( $items, $args ){

    //change theme location with your them location name
    if( is_admin() || $args->theme_location != 'top-menu' )
    return $items;

    $redirect = ( is_home() ) ? false : get_permalink();
    if( is_user_logged_in( ) ){

        $user=wp_get_current_user();
        $name=$user->display_name; // or user_login , user_firstname, user_lastname

        $link = '<a href="' . wp_logout_url( $redirect ) . '" title="' . __( 'Logout' ) .'">' . __( 'প্রস্থান' ) . '</a><a href="' . get_author_posts_url($user->ID) . '>' .$name. '</a>';
    }
    else{
        $link = '<a href="' . wp_login_url( $redirect ) . '" title="' . __( 'Login' ) .'">' . __( 'প্রবেশ' ) . '</a><a href="' . wp_registration_url($redirect) . '" title="' . __( 'Register' ) .'">' . __( 'নিবন্ধন' ) . '</a>';
    }
    return $items.= '<li id="log-in-out-link" class="menu-item menu-type-link">'. $link . '</li>';
}
add_filter( 'wp_nav_menu_items', 'add_login_out_item_to_menu', 50, 2 );