Need help with translatable string in template file

Hello Support,
I try to modify the portfolio grid single item output of the so called “AJAX Portfolio” the file I try to modify is:
config-tamplatebuilder/avia-shortcodes/portfolio.php

1 Question/Problem:
I want to show custom field content under the Image that shows to the left side of the content container. My client always has the same image size and always only 1 image so the space under this image is just blank and I want to show some additional data there.
I Installed an addon for the custom fields and I successfully included the custom fields output in the portolio.php file where I want it to show.

What is not working: The custom field value is translatable (WPML) but for the field title I need to put translatable strings in the php file but they don’t show in front-end, the values show fine.

This is what I have in the portfolio.php:

$output .= _e('Certification Prerequisites', "dive-data") .$divedata1. '</br>';
$output .= _e('Open Water Dives', 'dive-data') .$divedata2. '</br>';

I also tried:

$output .= __('Certification Prerequisites', "dive-data") .$divedata1. '</br>';
$output .= __('Open Water Dives', 'dive-data') .$divedata2. '</br>';

The $divedata1-8 show fine but the translatable strings do not show at all. In WPML String translation the strings are recognized correctly.

Question N°2:
Why is this file in question (portfolio.php) not recognized when I place it in my child theme folder (same folder structure as in ENOLD theme)?

Thanks
Gregor