Sorry, I found myself what was silly :-S It’s often while asking something that you found the solution, which is obvioulsly :
<?php if( get_field('status') == 'no'): ?>
<div class="side-button">
<a href="<?php the_field('the_link', get_the_ID()) ?>" target="_blank">Click the link</a>
</div>
<?php elseif ( get_field('status') == 'yes' ): ?>
<div class="side-button-dark">
Special message
</div>
<?php endif; ?>
Sorry, but I don’t find where to delete thread…
