Get Post by query like category_name, post_type etc 

            $blog_posts = new WP_Query( array( 'post_type' => 'post', 'post_status’' => 'publish', 'posts_per_page' => 3,'category_name' => 'case-study') );
            if ( $blog_posts->have_posts()){
                while ( $blog_posts->have_posts() ) {
                    $blog_posts->the_post();
                } 
                get_template_part( 'template-parts/content', get_post_type() );  
            }