The mistake in the php code when I create Templeate for WordPress

Warning: Trying to access array offset on value of type null in /var/www/u2016481/data/www/miostagroup.com/wp-content/themes/miosta/page-articles.php on line 32

but my code is

 if (!defined('ABSPATH')) {
  die();
}

$id = get_the_ID();
$event = get_field('content', $id);
/// print_r($home);
?>
<?php get_header(); ?>
<main class="main" data-page="home" id="smooth-content">
  <!-- header -->
  <?php get_template_part('template-parts/header/header_main'); ?>

  <div class="main__wrap">
    <div class="events__cover">
      <div class="events__cover-content activation">
        <h2 class="cover__content-title title__logo title__logo--57">
      32 line    <?php echo preg_replace("#*{2}(.*?)*{2}#", "<sup>$1</sup>", $event['title']); ?>
        </h2>
        <h1 class="cover__content-title title__logo title__logo--90">
          <?php echo get_the_title($id); ?>
        </h1>
      </div>
      <span class="events__cover-circle activation"></span>
      <span class="events__cover-circle activation events__cover-circle--type2"></span>
    </div>
    <section class="events__content">
      <?php
      $paged = (get_query_var('paged')) ? get_query_var('paged') : 1;
      $query = new WP_Query(array(
        'post_type' => 'post',
        'posts_per_page' => 6,
        'paged' => $paged
      ));
      if ($query->have_posts()) {
      ?>
        <div class="events__grid activation">

          <?php foreach ($query->posts as $k) {  ?>
            <?php
            $field = get_field('content', $k->ID);
            $year = date('j F Y', strtotime($k->post_date));
            ?>
            <div class="events__card" itemscope itemtype="http://schema.org/Event">
              <div class="events__card-photo">
                <picture>
                  <?php if (isset($field['img_prev']) && $field['img_prev']) { ?>
                 <?php echo avif_convert($field['img_prev']); ?>
                    <img class="events__card-img active" src="<?php echo $field['img_prev']['sizes']['medium']; ?>" alt="<?php echo ($field['img_prev']['alt'] ?? ""); ?>" data-tab="h" itemprop="image">
                  <?php } //end if 
                  ?>
                </picture>
              </div>
              <div class="events__card-content">
                <span class="events__card-date" itemprop="startDate"><?php echo month_translate($year); ?></span>
                <h2 class="events__card-title" itemprop="name"><?php echo ($k->post_title ?? ""); ?></h2>
                <a class="button main__products-link active" href="<?php echo get_permalink($k->ID); ?>" itemprop="url">
                  <span class="button__mask2"><?php pll_e('Подробнее'); ?></span>
                </a>
              </div>
            </div>
          <?php } //end foreach 
          ?>


        </div>



        <div class="events__pagi">

          <?php

          $big = 999999999; // Число, которое гарантированно больше числа всех страниц
          $pagination = paginate_links(array(
            'base' => str_replace($big, '%#%', esc_url(get_pagenum_link($big))),
            'show_all' => true,
            'prev_next' => false,
            'format' => '?paged=%#%',
            'current' => max(1, get_query_var('paged')),
            'total' => $query->max_num_pages,
            'type' => 'array',
          ));

          if ($pagination !== null) {

          ?>
            <a class="events__pagi-btn" href="<?php echo get_previous_posts_page_link(); ?>" aria-label="Предыдущая страница">
              <svg width="18" height="7">
                <use xlink:href="#icon-pagi-left">
                </use>
              </svg>
            </a>

            <ul class="events__pagi-list">

              <?php
              foreach ($pagination as $page) {
                $page = str_replace('page-numbers', 'events__pagi-link', $page);

                if (strpos($page, 'current')) {

                  $page = str_replace('current', 'active', $page);

                  echo '<li class="events__pagi-item">' .
                    $page
                    . '</li>';
                } else {

                  echo '<li class="events__pagi-item">' .
                    $page
                    . '</li>';
                }
              }
              ?>


            </ul>

            <a class="events__pagi-btn next" href="<?php echo get_next_posts_page_link(); ?>" aria-label="Следующая страница">
              <svg width="18" height="7">
                <use xlink:href="#icon-pagi-right">
                </use>
              </svg>
            </a>
          <?php } //end if $pagination null 
          ?>

        </div>
      <?php } //end if $query 
      ?>
      <span class="events__grid-circle"></span>
    </section>

  </div>
  <!-- footer -->
  <?php get_template_part('template-parts/footer/footer_main'); ?>
</main>
<?php get_footer(); ?>

What is wrong
It is a cooperated code from other web page with the same meaning is the same as in the other,but I have to do some kind of information
I did not understand what I need to do could you help me please?