ACF Query Structure

So you want to check if a field from acf has a value and if thats true you want to display it.
You can do it with this:

if( get_field( 'video' ) ) {

    ?>

        <video width="320" height="240" controls>

            <source src="https://wordpress.stackexchange.com/questions/292287/<?php echo get_field("video' ); ?>" type="video/mp4">

        </video>

    <?php

}else{


    the_post_thumbnail('', array('class' => 'img-responsive'));

}

This checks the field with name ‘video’ for a value. If there is a value it will display the video. If there is no video it will display an image instead.

Here is the code added in your own code:

    <?php 
       // the query
       $the_query = new WP_Query( array(
        'category' => 'Publish',
        'category__not_in' => 36 ,
        'orderby' => 'rand',
        'order'   => 'ASC',
         'posts_per_page'=>'12'
       )); 
    ?>
    <div class="">
    <?php if ( $the_query->have_posts() ) : ?>
      <?php while ( $the_query->have_posts() ) : $the_query->the_post(); ?>
    <div class="col-md-4 col-sm-4 col-xs-12 reason">
        <h2 class="postheader"><?php the_title(); ?>    
        </h2>
    <a target="blank" href="https://wordpress.stackexchange.com/questions/292287/<?php the_field("url'); ?>"><?php 

if( get_field( 'video' ) ) {

    ?>

        <video width="320" height="240" controls>

            <source src="https://wordpress.stackexchange.com/questions/292287/<?php echo get_field("video' ); ?>" type="video/mp4">

        </video>

    <?php

}else{

    the_post_thumbnail('', array('class' => 'img-responsive'));

}?></a>
        <br><?php the_excerpt(); ?> <a class="postlink" target="blank" href="https://wordpress.stackexchange.com/questions/292287/<?php the_field("url'); ?>">Read more</a>
      </div>
      <?php endwhile; ?>
      <?php wp_reset_postdata(); ?>
    <?php else : ?>
      <p><?php __('No News'); ?></p>
    <?php endif; ?>
    </div>

You still need to change the ACF field name of ‘video’ in the code to your field name.

tech