Replacing ACF with default WordPress post meta

template.php

<!--Accordion Section-->
<?php
/*
* This is an example of ACF repeater field whose name is "Content Accordion"
* and has sub fields: "Accordion Title" & "Accordion Content"
*/
$accordions = get_post_meta( get_the_ID(), 'content_accordion', TRUE );
if ( $accordions ) {
  ?>
  <div class="container">
    <div class="row">
      <div class="col-12">
        <div class="accordion" id="accordionModule">
          <?php
          for ( $i = 0; $i < $accordions; $i ++ ) {
            //use meta name as wrapper-name+array-key/number+field-name
            $title   = get_post_meta( get_the_ID(), 'content_accordion_' . $i . '_accordion_title', TRUE );
            $content = get_post_meta( get_the_ID(), 'content_accordion_' . $i . '_accordion_content', TRUE );
            $content = apply_filters('the_content', $content); //get content from WYSIWYG editors
            ?>
            <div class="card">
              <a class="btn-link <?= ( $i == 0 ) ? 'collapsed' : '' ?>"
                 data-toggle="collapse" data-target="#collapse<?= $i ?>"
                 aria-expanded="<?= ( $i == 0 ) ? 'true' : 'false' ?>"
                 aria-controls="collapse<?= $i ?>">
                <div class="card-header" id="heading<?= $i ?>>">
                  <h5 class="mb-0 font-thin accordion-title">
                    <?= $title ?>
                    <i class="fal down-arrow"></i>
                  </h5>
                </div>
              </a>
              <div id="collapse<?= $i ?>" class="collapse <?= ( $i == 0 ) ? 'show' : '' ?>"
                   aria-labelledby="heading<?= $i ?>" data-parent="#accordionModule">
                <div class="card-body">
                  <?= $content ?>
                </div>
              </div>
            </div>
            <?php
          }
          ?>
        </div>
      </div>
    </div>
  </div>
  <?php
}
?>
<!--End Accordion Section-->

make sure to DISABLE ACF ON FRONT-END
https://gist.github.com/utkrishta/c9853a10e1b48111f829a3ee8e0b6080