Thank you Kostas will check it now.

Okay Kostas this is your solution:

You can add this to your theme funcions.php file: 

add_action('wp_head', function() {
    ?>
    <style>
        .service-icon .far,
        .service-icon .fas {
            font-size: 40px;
            margin-bottom: 15px;
            color:#61b9ed;
        }
    </style>
    <?php
});

or just add this css in your style file:

.service-icon .far,
        .service-icon .fas {
            font-size: 40px;
            margin-bottom: 15px;
            color:#61b9ed;
        }

This will add styles to the Font Awesome 5.0 icons.

Great!

You can customize it of course if need add more styles. The problem here is that your theme and to be honest most of the themes are still using old version of Font Awesome while we are trying to keep the plugin up to date.

Look like it will take some time before the themes are update to Font Awesome 5 because it's really offering more including premium icons.

Good luck with your project!