How to get the post content from a category on my homepage

Is it really necessary to echo so much. If you make proper use of opening and closing php tags you can eliminate using echo. And why are you echoing get_the_title() when there is a build in feature for that. the_title() does exactly the same.

You can use WP_Query to create a special loop to get posts from a specific category. Just remember to reset your loop as you are going to start a new loop. For multiple loops, also check The Loop. One word of advice, the author of this page used query_posts, which you must not use at all, use WP_Query

As for the excerpt, you can change the read more link as follow

function new_excerpt_more( $more ) {
    return ' <---the code of your button here--->';
}
add_filter( 'excerpt_more', 'new_excerpt_more' );

So in the end, your code should like like this

<?php $my_query = new WP_Query('category_name=special_cat&posts_per_page=10'); ?>

<?php while ($my_query->have_posts()) : $my_query->the_post(); ?>

<section class="row"><div class="container-item">
            <div class="item">
            <div class="item-overlay">
            <div class="item-content">
            <div class="item-top-content">
            <div class="item-top-content-inner">
            <div class="item-product">
            <div class="item-top-title">
            <h2>
            <?php the_title(); ?>
            </h2><p class="subdescription">
            <?php the_excerpt(); ?>
            </p></div></div></div>
            </div>
            </div>
            </div>
            </div>
        </div>
</section>

<?php endwhile; ?>
<?php rewind_posts(); ?>

<---Start your new loop here --->