If your relationship field allows more than one value then it will return an array of ID’s and if you are only returning the IDs then you don’t need $post->
you only use this when using setup_postdata()`
$ids = get_field('conference_talks', false, false);
foreach ($ids as $id) {
$value = get_field('my_acf_field_name', $id);
}
All of this is explained in the documentation https://www.advancedcustomfields.com/resources/relationship/