<?php
function testi_loop()
{
    $arg = array(
        'post_type' => 'testimonial',
        'posts_per_page' => -1,
    );
    $testiPost = new WP_Query($arg); ?>
    <div class="testimonials-slider">
        <?php if ($testiPost->have_posts()): ?>
            <?php while ($testiPost->have_posts()): ?>
                <?php $testiPost->the_post();
                $url = wp_get_attachment_url(get_post_thumbnail_id($testiPost->ID)); ?>
                <div class="testi-inn">
                    <img src="<?php the_field('company_logo'); ?>" alt="">
                    <div class="testi-cont">
                        <?php the_content(); ?>
                    </div>
                    <div class="client-picture">
                        <img src="<?php echo $url; ?>" alt="testiProfile">
                        <h2>
                            <?php the_title(); ?>
                        </h2>
                    </div>
                </div>
            <?php endwhile; ?>
        <?php endif; ?>
    </div>
    <?php
    wp_reset_postdata();
}
add_shortcode('testi', 'testi_loop');
?>