Bootstrap 4 Dropdown Menu appears to the right of parent - css

Question

I'm newer to Bootstrap and have a question about my Navbar.
Here is my test site. TEST-DOMAIN
I'm currently using Bootstrap 4.3.1 with JQuery 3.4.1.
Menu looks and functions great on Desktop. Dropdown appears as expected. I added columns to the dropdown to make a Mega Menu of sorts.
When the site transitions over to mobile, the dropdown is appearing to the RIGHT of the parent menu item. Is there a way to make it appear BELOW the parent item and push the rest of the menu down below it?
I tried setting the dropdown to Display: absolute as found in other posts about this. But, while it shifts the dropdown to the left like I want, it floats it overtop of the rest of the menu. I would like it to align left, while pushing the rest of the menu below it.
Thanks for any help!
* EDIT - Adding code *
<!--Navbar-->
<nav id="navbar" class="navbar navbar-expand-lg navbar-dark nav-transparent sticky-top">
<div class="container">
<button class="navbar-toggler navbar-toggler-right" type="button" data-toggle="collapse" data-target="#navbarNav" aria-controls="navbarNav" aria-expanded="false" aria-label="Toggle navigation">
<span class="navbar-toggler-icon"></span>
</button>
<a class="navbar-brand" href="#" style="margin-top: -5px;"><strong>Test Website</strong></a>
<div class="collapse navbar-collapse" id="navbarNav">
<ul class="navbar-nav mr-center">
<li class="nav-item active">
<a class="nav-link" href="home.html">Home <span class="sr-only">(current)</span></a>
</li>
<li class="nav-item dropdown btn-group">
<a class="nav-link dropdown-toggle" id="dropdownMenu1" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">Services</a>
<div class="dropdown-menu dropdown" aria-labelledby="dropdownMenu1">
<div class="container">
<div class="row">
<div class="col-md-4">
<a class="dropdown-item" href="another-page.html">ANOTHER PAGE</a>
<a class="dropdown-item" href="pools.html">POOLS</a>
<a class="dropdown-item" href="test-10.html">TEST 10</a>
<a class="dropdown-item" href="test-5.html">TEST 5</a>
</div>
<div class="col-md-4">
<a class="dropdown-item" href="test-6.html">TEST 6</a>
<a class="dropdown-item" href="test-7.html">TEST 7</a>
<a class="dropdown-item" href="test-8.html">TEST 8</a>
<a class="dropdown-item" href="test-9.html">TEST 9</a>
</div>
<div class="col-md-4">
<a class="dropdown-item" href="yet-another-page.html">YET ANOTHER PAGE</a>
<a class="dropdown-item" href="awesome-page.html">AWESOME PAGE</a>
</div>
</div>
</div>
</div>
</li>
<li class="nav-item"><a class="nav-link" href="about.html">About Us</a></li>
<li class="nav-item"><a class="nav-link" href="gallery.html">Gallery</a></li>
<li class="nav-item"><a class="nav-link" href="faq.html">FAQ</a></li>
<li class="nav-item"><a class="nav-link" href="kitchen-vision.html">KITCHEN VISION</a></li>
<li class="nav-item"><a class="nav-link" href="contact.html">Contact Us</a>
</li>
</ul>
</div>
</div>
I've removed all my custom CSS for the NavBar to make sure I wasn't doing something incorrect with my edits.

Answer 1

#media screen and (max-width: 768px) {
.mx-auto.d-flex {
margin: 0!important;
justify-content: space-between;
display: flex;
width: 100vw;
}
}
<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/css/bootstrap.min.css" integrity="sha384-ggOyR0iXCbMQv3Xipma34MD+dH/1fQ784/j6cY/iJTQUOhcWr7x9JvoRxT2MZw1T" crossorigin="anonymous">
<nav class="navbar navbar-expand-lg navbar-light bg-light sticky-top">
<div class="mx-auto d-flex">
<a class="navbar-brand" href="#">Test Website</a>
<button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarSupportedContent" aria-controls="navbarSupportedContent" aria-expanded="false" aria-label="Toggle navigation">
<span class="navbar-toggler-icon"></span>
</button>
<div class="collapse navbar-collapse" id="navbarSupportedContent">
<ul class="navbar-nav ">
<li class="nav-item active">
<a class="nav-link" href="#">Home <span class="sr-only">(current)</span></a>
</li>
<li class="nav-item dropdown">
<a class="nav-link dropdown-toggle" href="#" id="navbarDropdown" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
Services
</a>
<div class="dropdown-menu" aria-labelledby="navbarDropdown">
<div class="container">
<div class="row">
<div class="col-md-4">
<a class="dropdown-item" href="another-page.html">ANOTHER PAGE</a>
<a class="dropdown-item" href="pools.html">POOLS</a>
<a class="dropdown-item" href="test-10.html">TEST 10</a>
<a class="dropdown-item" href="test-5.html">TEST 5</a>
</div>
<div class="col-md-4">
<a class="dropdown-item" href="test-6.html">TEST 6</a>
<a class="dropdown-item" href="test-7.html">TEST 7</a>
<a class="dropdown-item" href="test-8.html">TEST 8</a>
<a class="dropdown-item" href="test-9.html">TEST 9</a>
</div>
<div class="col-md-4">
<a class="dropdown-item" href="yet-another-page.html">YET ANOTHER PAGE</a>
<a class="dropdown-item" href="awesome-page.html">AWESOME PAGE</a>
</div>
</div>
</div>
</div>
</li>
<li class="nav-item"><a class="nav-link" href="about.html">About Us</a></li>
<li class="nav-item"><a class="nav-link" href="gallery.html">Gallery</a></li>
<li class="nav-item"><a class="nav-link" href="faq.html">FAQ</a></li>
<li class="nav-item"><a class="nav-link" href="kitchen-vision.html">KITCHEN VISION</a></li>
<li class="nav-item"><a class="nav-link" href="contact.html">Contact Us</a>
</li>
</ul>
</div>
</div>
</nav>