The site has a taxonomy: my_taxonomy. I need to get the total amount of sales for each custom product taxonomy, list for level 1 and for level 2, I mean it:
Level0
-level1 <– this
–level2 <– this
—level3
–level2 <– this
-level1 <– this
–level2 <– this
—level3
—level3

I did it like this:

function handle_csv_export()
{

  if (! wp_verify_nonce($_POST['_wpnonce'], 'generate-csv')) {
    return;
  }

  $orders = wc_get_orders(array(
    'limit' => -1,
    'status' => array('completed', 'processing', 'on-hold')
  ));

  $levels1 = $levels2 = array();
  foreach (get_terms('my_taxonomy', array('hide_empty' => false, 'parent' => 0)) as $parent_term) {
    foreach (get_terms('my_taxonomy', array('hide_empty' => false, 'parent' => $parent_term->term_id)) as $child_term) {
      $levels1[] = array("value" => $child_term->term_id, "label" => $child_term->name); //get level1
      foreach (get_terms('my_taxonomy', array('hide_empty' => false, 'parent' => $child_term->term_id)) as $third_term) {
        $levels2[] = array("value" => $third_term->term_id, "label" => $third_term->name); //get level2
      }
    }
  }


  $level1_amount_result = $level2_amount_result = array();

  foreach ($orders as $order) {
    $items = $order->get_items();

    foreach ($items as $item) {
      $product_id = $item->get_product_id();

      foreach ($levels1 as $level1) {
        if (has_term($level1['value'], 'my_taxonomy', $product_id)) {
          $level1_amount_result[$level1['label']] += $item->get_total(); //adding up the price for each taxonomy
        }
      }
      foreach ($levels2 as $level2) {
        if (has_term($level2['value'], 'my_taxonomy', $product_id)) {
          $level2_amount_result[$level2['label']] += $item->get_total();
        }
      }
    }

  }

  // add to csv
  $filetime = time();

  $list = array(
    array("levels1"),
  );

  foreach ($level1_amount_result as $level1_name => $level1_amount) {
    array_push($list, array($level1_name, $level1_amount . '$'));
  }

  array_push($list, array("levels2"));

  foreach ($level2_amount_result as $level2_name => $level2_amount) {
    array_push($list, array($level2_name, $level2_amount . '$'));
  }

  $upload_dir = wp_upload_dir();
  $file_path = $upload_dir['basedir'] . '/myorders/myorders' . $filetime . '.csv';
  $folder_path = $upload_dir['basedir'] . '/myorders';
  if (!file_exists($folder_path)) {
    mkdir($folder_path, 0777);
  }
  $files = glob($folder_path . '/*');

  foreach ($files as $file) {
    if (is_file($file)) {
      unlink($file);
    }
  }

  header('Content-Type: text/csv');
  header('Content-Disposition: attachment; filename="export.csv"');

  $file = fopen($file_path, "w");

  foreach ($list as $line) {
    fputcsv($file, $line);
  }
  readfile($file_path);
  fclose($file);
  exit;
}

https://prnt.sc/BEvAcv34kgqZ

It seems to work with a small number of orders, but the site has many values ​​in the taxonomy and many orders, the code takes a long time to execute and the site crashes. How can I speed up this process? Thanks.