Problem with making the hero section of this site responsive - html

Question

I'm experiencing problems on why the hero section which I'm building isn't responsive, I'm using bootstrap and the grid system, the image I the hero section is responsive as I'm using the class img-fluid but the text and buttons don't follow suit I'm really confused to where I've gone wrong and help would be massively appreciated as I've been banging my head against a wall for an hour on end now.
here's the HTML:
<!-- ======= Header ======= -->
<header id="header" class="fixed-top">
<div class="container d-flex align-items-center">
<img src="assets/img/logo.png">
<!-- Uncomment below if you prefer to use an image logo -->
<!-- <img src="assets/img/logo.png" alt="">-->
<nav class="nav-menu d-none d-lg-block">
<ul>
<li class="active">Home</li>
<li>About</li>
<li>Services</li>
<li>Portfolio</li>
<li>Team</li>
<li class="drop-down">Drop Down
<ul>
<li>Drop Down 1</li>
<li class="drop-down">Deep Drop Down
<ul>
<li>Deep Drop Down 1</li>
<li>Deep Drop Down 2</li>
<li>Deep Drop Down 3</li>
<li>Deep Drop Down 4</li>
<li>Deep Drop Down 5</li>
</ul>
</li>
<li>Drop Down 2</li>
<li>Drop Down 3</li>
<li>Drop Down 4</li>
</ul>
</li>
<li>Contact</li>
</ul>
</nav><!-- .nav-menu -->
</div>
</header><!-- End Header -->
<!-- ======= Hero Section ======= -->
<section id="hero" class="d-flex align-items-center">
<div class="container" data-aos="zoom-out" data-aos-delay="100">
<div class="hero-image">
<img src="assets/img/hero-img.png" class="img-fluid">
</div>
<div class="hero-textbox">
<h2 class="hero-heading-text">WINNING WITH DATA:<br>
CRM AND ANALYTICS FOR THE BUSINESS OF <br>SPORTS</h2>
<p class="hero-description-text">Suitable for beginners, intermediaries or digital marketers who haven't yet included data-driven decision making in their approach. Our book provides a fantastic start for those looking to understand the role of CRM and Business Intelligence for the sports industry.</p>
<span class="glyphicon glyphicon-shopping-cart"></span> Order Now
</div>
</div>
</section><!-- End Hero -->
here's the CSS:
https://pastebin.com/F3ghpywz
Thank you so much in advance for helping me solve this problem.
Kind regards,
Josh.