foreach in foreach

Hi,
I got stuck at this problem, I need to make a custom menu of portfolio-items, that goes Portfolio -> categories -> items from the category. Unfortunately, it shows all the portfolio-items instead of just from the category.
Thanks for your help
The site: https://www.brightthemes.8u.cz

<?php
if ( !function_exists( 'brighttheme_portfolio_filtering' ) ) {
        function brighttheme_portfolio_filtering() {

            $brighttheme_portfolio_filtering_html = '

                    <li id="menu-item" class="menu-item"><a href="#"> <span>'. esc_html__('PORTFOLIO','brighttheme') .'</span> </a> 

                      ';
                        foreach ( get_terms('category') as $category ){
                            $brighttheme_portfolio_filtering_html .= '<li id="menu-item" class="menu-item"><a href="#" data-filter=".'
                                                                    .'">'. ( $category->name )
                                                                    .'<ul class="sub-menu">';
                        $args = array('post_type' => 'portfolio',
                            'category' => $category, );

                       $portfolios = get_pages($args); 

                        foreach ( $portfolios as $portfolio_item ){
                            $brighttheme_portfolio_filtering_html .= '<li id="menu-item" class="menu-item"><a>ID ) .'" data-filter=".';
                            $brighttheme_portfolio_filtering_html .= get_page_link( $portfolio_item ->ID ) .'">'. $portfolio_item ->post_title;
                            $brighttheme_portfolio_filtering_html .= '</a>';
                        }
                        $brighttheme_portfolio_filtering_html .= '
                         ';
                        }
                      $brighttheme_portfolio_filtering_html .= '
                   ';
            echo $brighttheme_portfolio_filtering_html;
        }
    }
?>