Below is a snippet of how to render a view inside a controller. You can easily add content below or above your view this way. Trick is to render it correctly!

<?php

namespace Drupal\mymodule\Controller;

use Drupal\Core\Controller\ControllerBase;
use Drupal\views\Views;

/**
 * Class ContestantsController.
 */
class ContestantsController extends ControllerBase {
  /**
   * Renders the contestants page.
   *
   * @return array
   *   The renderable array.
   */
  public function render() {

    $activeContestId = 100; // 
    $view = Views::getView('mymodule_contestants');
    $view->setDisplay('block_1');
    // contextual relationship filter
    $view->setArguments([$activeContestId]);
    $view->execute();
    $rendered = $view->render();
    $output = \Drupal::service('renderer')->render($rendered);

    return [
      ['#markup' => $output]
    ];
  }

  public function title() {
    return $this->t('Contestants');
  }
}