The parallax effect in my carousel has issues - html

Question

I want to include three carousels on my website, which should be full height and should have a parallax effect. I have a code snippet I found some time ago, and it just doesn't work. The parallax effect is not working, and the pictures don't display in full height.
Here is my html code:
<div id="carousel" class="carousel slide carousel-fade" data-ride="carousel" data-interval="6000">
<ol class="carousel-indicators">
<li data-target="#carousel" data-slide-to="0" class="active"></li>
<li data-target="#carousel" data-slide-to="1"></li>
<li data-target="#carousel" data-slide-to="2"></li>
</ol>
<div class="carousel-inner" role="listbox">
<div class="carousel-item active">
<a href="learnmore.html">
<div class="jumbotron paral paralsec">
<h1 class="display-3">Customer orientation</h1>
<p class="lead">Every product is individually customized to your needs</p>
</div>
</a>
</div>
<!-- /.carousel-item -->
<div class="carousel-item">
<a href="lenses.html">
<!-- Second Parallax Section -->
<div class="jumbotron paral paralsec1">
<h1 class="display-3">Customer orientation</h1>
<p class="lead">Your project is at the center of our process chains</p>
</div>
</a>
</div>
<!-- /.carousel-item -->
<div class="carousel-item">
<a href="lmkposition.html">
<!-- Third Parallax Section -->
<div class="jumbotron paral paralsec2">
<h1 class="display-3">Customer orientation</h1>
<p class="lead">All our services are supported by our support team which is always there for you</p>
</div>
</a>
</div>
<!-- /.carousel-item -->
</div>
<!-- /.carousel-inner -->
<a class="carousel-control-prev" href="#carousel" role="button" data-slide="prev">
<span class="carousel-control-prev-icon" aria-hidden="true"></span>
<span class="sr-only">Previous</span>
</a>
<a class="carousel-control-next" href="#carousel" role="button" data-slide="next">
<span class="carousel-control-next-icon" aria-hidden="true"></span>
<span class="sr-only">Next</span>
</a>
</div>
And here is my CSS code:
.carousel, .slide,
.carousel .carousel-inner,
.carousel .carousel-item,
.carousel .carousel-item img,
.carousel .carousel-control {
border-radius: 0px;
overflow: hidden;
}
/ Header Parallax Element Style/
.paral {
min-height: 900px;
background-attachment: fixed;
background-size: cover;
background-position: 50% 50%;
}
/ Paragraph for Parallax Section /
.paral p {
font-size: 24px;
color:#f5f5f5;
text-align: center;
line-height: 60px;
}
/ Heading for Parallax Section /
.paral h1 {
color: rgba(255, 255, 255, 0.8);
font-size: 60px;
text-align: center;
padding-top: 60px;
line-height: 100px;
}
/ Image for Parallax Section /
.paralsec {
background-image: url(img/customer.jpg);
background-size: 100% !important;
}
.paralsec1 {
background-image: url(img/customer.jpg);
height: 100%;}
.paralsec2 {
background-image: url(img/customer.jpg);
height: 100%;}
.paralsec3 {
background-image: url(img/process.jpg);
}
.paralsec4 {
background-image: url(img/process.jpg);}
.paralsec5 {
background-image: url(img/process.jpg);}
.paralsec6 {
background-image: url(img/quality.jpg);}
.paralsec7 {
background-image: url(img/quality.jpg);}
.paralsec8 {
background-image: url(img/quality.jpg);}
/ Add more images for more sections /
/ Remove Bottom Margin from Jumbotron /
.jumbotron{margin-bottom: 0;}
.values {
text-align: center;
display: block;
margin-left: auto;
margin-right: auto;
}
As you can see, I tried to change some values of the image size, but to no avail. Also, only the first image of my carousel is showing, and the carousel has border even though I tried to erase them.
The CSS is for all three carousels, but I only included the html code of one since they are the same, and the first is the one making the most problems.