Use WP_Query for getting the posts you want. Then you can loop through them and get their title, their featured image and their excerpt to be printed they way you want. Something like that:
<?php $args = [
'post_type' => 'post',
'post_status' => 'publish',
'posts_per_page' => 9,
'order' => 'DESC',
'orderby' => 'date',
]; ?>
<?php $the_query = new WP_Query( $args ); ?>
<?php if ( $the_query->have_posts() ) : ?>
<div class="my-grid">
<?php while ( $the_query->have_posts() ) : $the_query->the_post(); ?>
<div class="grid-item">
<div class="thumbnail"><?php the_post_thumbnail(); ?></div>
<div class="title"><?php the_title(); ?></div>
<div class="excerpt"><?php the_excerpt(); ?></div>
</div>
<?php endwhile; ?>
<?php wp_reset_postdata(); ?>
</div>
<?php else : ?>
<p><?php esc_html_e( 'Sorry, no posts matched your criteria.' ); ?></p>
<?php endif; ?>
And the rest is just CSS.