Centering a Carousel Modal - css

Question

I created a carousel modal for Bootstrap and can't figure out how to properly center it regardless of screensize or if for example a mobilescreen is tilted vertically.
The CSS Code I have right now properly spaces the modal on a normal pc screen, but it doesnt work on mobile screen and the MOdal appears on the top of the screen instead of appearing in the middle as it should. neither
position
nor
vertical-alignment
worked for me.
.modal {
vertical-align: middle;
padding-left: 5%;
padding-left: 5%;
padding-top: 1%;
text-align: middle;
max-height: 90vh;
max-width: 95vw;
}
.modal .carousel-inner {
max-height: 100% ! important;
position: center;
text-align: middle;
vertical-align: middle;
}
.modal .carousel .item #media (max-width: 991px) {
.modal {
padding-top: 55%;
}
}
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" integrity="sha384-Gn5384xqQ1aoWXA+058RXPxPg6fy4IWvTNh0E263XmFcJlSAwiGgFAW/dAiS6JXm" crossorigin="anonymous">
<script src="https://code.jquery.com/jquery-3.2.1.slim.min.js" integrity="sha384-KJ3o2DKtIkvYIK3UENzmM7KCkRr/rE9/Qpg6aAZGJwFDMVNA/GpGFF93hXpG5KkN" crossorigin="anonymous"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.12.9/umd/popper.min.js" integrity="sha384-ApNbgh9B+Y1QKtv3Rn7W3mgPxhU9K/ScQsAP7hUibX39j7fakFPskvXusvfa0b4Q" crossorigin="anonymous"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js" integrity="sha384-JZR6Spejh4U02d8jOt6vLEHfe/JQGiRRSQQxSfFWpi1MquVdAyjUar5+76PVCmYl" crossorigin="anonymous"></script>
<!-- Page Content -->
<div class="container">
<h1 class="my-4 text-center text-lg-left" style="padding-bottom:3%;padding-left:0%">Gallerie</h1>
<div class="row text-center text-lg-left">
<div class="col-lg-3 col-md-4 col-xs-6">
<a href="#" class="d-block mb-4 h-100">
<img class="img-fluid img-thumbnail" src="http://placehold.it/400x300" alt="" data-toggle="modal" data-target="#Gallerie">
</a>
</div>
<div class="col-lg-3 col-md-4 col-xs-6">
<a href="#" class="d-block mb-4 h-100">
<img class="img-fluid img-thumbnail" src="http://placehold.it/400x300" alt="">
</a>
</div>
<div class="col-lg-3 col-md-4 col-xs-6">
<a href="#" class="d-block mb-4 h-100">
<img class="img-fluid img-thumbnail" src="http://placehold.it/400x300" alt="">
</a>
</div>
<div class="col-lg-3 col-md-4 col-xs-6">
<a href="#" class="d-block mb-4 h-100">
<img class="img-fluid img-thumbnail" src="http://placehold.it/400x300" alt="">
</a>
</div>
<div class="col-lg-3 col-md-4 col-xs-6">
<a href="#" class="d-block mb-4 h-100">
<img class="img-fluid img-thumbnail" src="http://placehold.it/400x300" alt="">
</a>
</div>
<div class="col-lg-3 col-md-4 col-xs-6">
<a href="#" class="d-block mb-4 h-100">
<img class="img-fluid img-thumbnail" src="http://placehold.it/400x300" alt="">
</a>
</div>
<div class="col-lg-3 col-md-4 col-xs-6">
<a href="#" class="d-block mb-4 h-100">
<img class="img-fluid img-thumbnail" src="http://placehold.it/400x300" alt="">
</a>
</div>
<div class="col-lg-3 col-md-4 col-xs-6">
<a href="#" class="d-block mb-4 h-100">
<img class="img-fluid img-thumbnail" src="http://placehold.it/400x300" alt="">
</a>
</div>
<div class="col-lg-3 col-md-4 col-xs-6">
<a href="#" class="d-block mb-4 h-100">
<img class="img-fluid img-thumbnail" src="http://placehold.it/400x300" alt="">
</a>
</div>
<div class="col-lg-3 col-md-4 col-xs-6">
<a href="#" class="d-block mb-4 h-100">
<img class="img-fluid img-thumbnail" src="http://placehold.it/400x300" alt="">
</a>
</div>
<div class="col-lg-3 col-md-4 col-xs-6">
<a href="#" class="d-block mb-4 h-100">
<img class="img-fluid img-thumbnail" src="http://placehold.it/400x300" alt="">
</a>
</div>
<div class="col-lg-3 col-md-4 col-xs-6">
<a href="#" class="d-block mb-4 h-100">
<img class="img-fluid img-thumbnail" src="http://placehold.it/400x300" alt="">
</a>
</div>
</div>
<div class="modal" id="Gallerie">
<div id="carouselExampleControls" class="carousel slide" data-ride="carousel">
<div class="carousel-inner">
<div class="carousel-item active">
<img class="d-block w-100" src="http://placehold.it/400x300" alt="First slide">
</div>
<div class="carousel-item">
<img class="d-block w-100" src="http://placehold.it/400x300" alt="Second slide">
</div>
<div class="carousel-item">
<img class="d-block w-100" src="http://placehold.it/400x300" alt="Third slide">
</div>
</div>
<a class="carousel-control-prev" href="#carouselExampleControls" 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="#carouselExampleControls" role="button" data-slide="next">
<span class="carousel-control-next-icon" aria-hidden="true"></span>
<span class="sr-only">Next</span>
</a>
</div>
</div>
</div>
<!--/Gallerie-->

Answer 1

The modal needs the proper structure as detailed the Bootstrap 4 docs. Just use modal-dialog-centered and you don't need the extra CSS...
https://www.codeply.com/go/BDNba719xE
<div class="modal" id="Gallerie">
<div class="modal-dialog modal-dialog-centered" role="document">
<div class="modal-content">
<div id="carouselExampleControls" class="carousel slide" data-ride="carousel">
<div class="carousel-inner">
<div class="carousel-item active">
<img class="d-block w-100" src="http://placehold.it/400x300" alt="First slide">
</div>
<div class="carousel-item">
<img class="d-block w-100" src="http://placehold.it/400x300" alt="Second slide">
</div>
<div class="carousel-item">
<img class="d-block w-100" src="http://placehold.it/400x300" alt="Third slide">
</div>
</div>
<a class="carousel-control-prev" href="#carouselExampleControls" 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="#carouselExampleControls" role="button" data-slide="next">
<span class="carousel-control-next-icon" aria-hidden="true"></span>
<span class="sr-only">Next</span>
</a>
</div>
</div>
</div>
</div>