How to add a prefix - suffix to a view title
The variables title_prefix and title_suffix will be rendered using Twig, and therefore filtered from markup and potentially harmful code.

If you like to use HTML within Twig variables, you need to use an instance of the Markup class:

use Drupal\Core\Render\Markup;

/**
 * Implements hook_preprocess_HOOK() for page_title.
 */
function mytheme_preprocess_page_title(array &amp;$variables) {
  $variables['title_prefix']['#markup'] = Markup::create('&lt;div class="row heading-section"&gt;&lt;div class="col-md-9 el-col-md-middle"&gt;&lt;div class="row"&gt;');
  $variables['title_suffix']['#markup'] = Markup::create('&lt;/div&gt;&lt;/div&gt;&lt;/div&gt;');
}


PS.: The above hook would add the markup to all titles. If this really is your intention, consider altering the page-title.html.twig template instead.