Portfolio posts and thumbnails

Hello!

I create website with that nice theme and added to childthemes single.php file following lines to be able to display feature image in single post view as well.
<?php if ( has_post_thumbnail() ):?>
<div class=”featured-image-wrap”><?php the_post_thumbnail(); ?></div>
<?php endif; ?>

Instead of thumbnail it displays huge image, it is way bigger then original image, so it becomes all blurry. Thumbnail size is set to 200px. What to do to display instead of big image the thumbnail?

Second question – how could I display post excerpt on portfolio page below the title? Currently it displays there only feature image + post title.