Get 20 posts from one category by slug

cat_loop.php

$args = array(
	'category_name'	=> 'slug',
	'posts_per_page'=> 20
);

$mis_posts = new WP_Query( $args );

while ( $mis_posts->have_posts() ) {
	$mis_posts->the_post();
	/**
	 *  the_title();
	 *  the_content();
	 */
}

wp_reset_postdata();