Hover (margin, z-index) button bug - html

Question

I am building a page and I have small bug here.I can't click and hover on my button (buttons in div slide with class btn).I think a problem is in z-index or in margin on some element. But I don't know how to solve that.
Here is a page: http://project.gmwebs.cz/ .
* {
box-sizing: border-box;
margin: 0;
padding: 0;
font-family: 'Cabin', sans-serif;
}
body {
background: url(img/background.jpg);
}
a {
text-decoration: none;
color: rgb(121, 0, 0);
}
h2 {
color: #F2F2F2;
}
/* Menu */
.kolecko{
width: 200px;
height: 100px;
background-color: #F2F2F2;
border-bottom-right-radius: 100px;
border-bottom-left-radius: 100px;
border: 10px solid rgb(121, 0, 0);
border-top: 0;
z-index: 3;
position: absolute;
-webkit-box-sizing: border-box;
-moz-box-sizing: border-box;
box-sizing: border-box;
margin-top: 40px;
}
.logo {
width: 160px;
z-index: 4;
position: absolute;
}
.menu-container {
display: flex;
justify-content: center;
align-items: center;
position: relative;
}
nav {
height: 90px;
background-color: #F2F2F2;
border-bottom: 10px solid rgb(121, 0, 0);
display: flex;
flex-direction: column;
align-content: center;
justify-content: center;
}
nav ul {
display: flex;
flex-direction: row;
align-content: center;
justify-content: center;
margin: 0 100px;
}
nav ul li{
list-style-type: none;
padding: 0 20px;
text-transform: uppercase;
color: rgb(121, 0, 0);
font-size: 1.5rem;
}
nav ul li a:hover {
color: #000;
}
.toggle {
width: 100%;
padding: 15px 20px;
background: rgb(121, 0, 0);
text-align: right;
box-sizing: border-box;
color: #fff;
font-size: 2rem;
display: none;
}
.ul-list {
display: flex;
align-content: center;
justify-content: center;
flex-direction: row;
}
#link-menu {
margin-right: 10%;
}
#phone {
margin-left: 10%;
}
nav .ul-list .social-btn li:nth-child(1) {
padding-right: 0px;
}
nav .ul-list .social-btn li:nth-child(2) {
padding-left: 7px;
}
.social-btn {
display: flex;
justify-content: center;
align-content: center;
flex-direction: row;
}
i.fab.fa-facebook-square {
color: #3b5992;
}
i.fab.fa-instagram {
background: radial-gradient(circle at 30% 107%, #fdf497 0%, #fdf497 5%, #fd5949 45%, #d6249f 60%, #285AEB 90%);
-webkit-background-clip: text;
/* Also define standard property for compatibility */
background-clip: text;
-webkit-text-fill-color: transparent;
}
/* Slider */
.slider {
display: block;
height: 100%;
width: 100%;
z-index: -1;
background-color: #1f1f1f;
overflow: hidden;
position: absolute;
top: 0px;
right: 0px;
border-bottom: 10px solid rgb(121, 0, 0);
}
.slider > * {
position: absolute;
display: block;
width: 100%;
height: 100%;
background-color: #1f1f1f;
animation: slide 12s infinite;
overflow: hidden;
}
.slide:nth-child(1) {
left: 0%;
animation-delay: -1s;
background-image: url(img/slide1.jpg);
background-size: cover;
background-position: center;
}
.slide:nth-child(2) {
left: 100%;
animation-delay: 3s;
background-image: url(img/slide2.png);
background-size: cover;
background-position: center;
}
.slide:nth-child(3) {
left: 100%;
animation-delay: 7s;
background-image: url(img/slide3.jpg);
background-size: cover;
background-position: center;
}
.slide p {
font-size: 2rem;
text-align: center;
display: inline-block;
width: 100%;
margin-top: 350px;
color: rgb(121, 0, 0);
background: 0% 0% no-repeat padding-box;
opacity: 0.84;
backdrop-filter: blur(30px);
-webkit-backdrop-filter: blur(30px);
padding-top: 20px;
z-index: 4;
}
.slide p span {
font-size: 1.5rem;
color: #000;
}
.btn {
background-color:transparent;
border:3px solid rgb(121, 0, 0);;
display:inline-block;
cursor:pointer;
color:rgb(121, 0, 0);
font-size: 1.5rem;
padding:5px 30px;
text-decoration:none;
margin: 20px 0;
}
.btn:hover {
background-color:transparent;
color: #000;
border:3px solid #000;
}
.btn:active {
position:relative;
top:1px;
}
#keyframes slide {
0% { left: 100%; width: 100%; opacity: 1;}
6.667% { left: 0%;}
33.334% { left: 0%;}
40% { left: -100%; width: 100%; opacity: 1;}
40.0001% { left: -100%; width: 0%; opacity: 0;}
100% { left: 100%; width: 0%; opacity: 1;}
}
/* Prolog */
.prolog {
text-align: center;
color: #F2F2F2;
margin: 10%;
margin-bottom: 5%;
font-size: 1.2rem;
margin-top: 102.5vh;
}
.prolog p {
margin-top: 1rem;
}
/* Newslatters */
.newslatters {
display: flex;
align-content: center;
justify-content: center;
flex-direction: column;
text-align: center;
color: #F2F2F2;
}
.newslatters form {
display: flex;
flex-direction: column;
justify-content: center;
align-content: center;
text-align: center;
margin: 1% 35%;
margin-top: 0%;
color: #F2F2F2;
}
.newslatters p {
margin: 0.5% 0%;
font-size: 1.2rem;
}
.newslatters h2 {
font-size: 1.8rem;
}
.newslatters form input.email {
margin: 1% 0;
padding: 2% 0%;
text-align: center;
font-size: 1rem;
background-color: #F2F2F2;
}
.newslatters form input.email:active {
border: 3px solid #000;
}
.newslatters form input.submit {
margin: 1% 25%;
margin-top: 5%;
border: 3px solid rgb(121, 0, 0);
padding: 1.3% 0%;
text-align: center;
font-weight: bold;
background-color: #F2F2F2;
font-size: 1rem;
box-shadow: 5px 10px transparent;
}
.newslatters form input:hover {
border: 3px solid #000;
}
/* Footer */
footer {
border-top: 5px solid rgb(121, 0, 0);
margin-top: 2%;
}
footer .author {
padding: 0.8% 0;
text-align: center;
color: #F2F2F2;
}
footer .author a{
font-weight: bold;
color: #F2F2F2;
}
footer .author a:hover{
color: rgb(121, 0, 0);
}
i.fas.fa-heart {
color: rgb(121, 0, 0);
}
/* Media Query */
#media (max-width: 1440px) {
nav ul li{
font-size: 1.3rem;
}
nav ul {
margin: 0 50px;
}
}
#media (max-width: 1024px) {
nav ul {
margin: 0 10px;
}
nav ul li{
font-size: 1rem;
}
footer .author {
padding: 1.5% 0;
text-align: center;
color: #F2F2F2;
}
}
#media (max-width: 1023px) {
.toggle {
display: block;
}
.kolecko {
display: none;
}
.active {
display: block;
}
.ul-list {
display: flex;
align-content: center;
justify-content: center;
flex-direction: column;
margin-top: 0px;
padding-top: 0px;
}
#link-menu {
margin-right: 0%;
height: 280px;
padding-bottom: 0px;
}
#phone {
margin-left: 0%;
}
#phone li:nth-child(2) {
border-bottom: none;
padding-top: 20px;
}
#phone .social-btn li:nth-child(1) {
border-bottom: none;
padding-right: 7px;
}
#phone .social-btn li:nth-child(2){
border-bottom: none;
padding-top: 0px;
}
.social-btn {
display: flex;
justify-content: center;
align-content: center;
flex-direction: row;
}
.logo {
z-index: 1;
position: absolute;
top: -400px;
}
nav {
height: auto;
background-color: #F2F2F2;
border-bottom: 10px solid rgb(121, 0, 0);
z-index:1;
display: none;
flex-direction: column;
align-content: flex-end;
justify-content: flex-end;
align-items: center;
}
nav ul {
display: flex;
flex-direction: column;
align-content: flex-end;
justify-content: flex-end;
text-align: center;
margin: 0px 0px;
z-index: 1;
padding-bottom: 20px;
}
nav ul li{
list-style-type: none;
padding: 0px 0px;
text-transform: uppercase;
color: rgb(121, 0, 0);
font-size: 1.5rem;
line-height: 1.4;
border-bottom: 1px #000 solid;
}
nav ul li:nth-child(2) {
margin-right: 0%;
}
nav ul li:nth-child(3) {
margin-left: 0%;
}
.slide p {
margin-top: 250px;
}
.prolog {
font-size: 1rem;
}
.newslatters form {
margin: 1% 20%;
font-size: 1rem;
}
.newslatters p {
font-size: 1rem;
}
.newslatters form input.submit {
padding: 1.3% 2%;
}
}
<link rel="stylesheet" href="https://use.fontawesome.com/releases/v5.13.1/css/all.css" integrity="sha384-xxzQGERXS00kBmZW/6qxqJPyxW3UR0BPsL4c8ILaIWXva5kFi7TxkIIaMiKtqV1Q" crossorigin="anonymous">
<div class="toggle">
<i class="fa fa-bars menu" aria-hidden="true"></i>
</div>
<nav>
<div class="ul-list">
<ul id="link-menu">
<li><i class="fas fa-home"></i> Domů</li>
<li><i class="fas fa-car"></i> Pronájem</li>
<li><i class="fas fa-dollar-sign"></i> Prodej</li>
</ul>
<ul id="phone">
<li><i class="fas fa-mobile-alt"></i> Kontakt</li>
<li><i class="fas fa-phone-square-alt"></i> [phone]</li>
<div class="social-btn">
<li><i class="fab fa-facebook-square"></i></li>
<li><i class="fab fa-instagram"></i></li>
</div>
</ul>
</div>
</nav>
<div class="menu-container">
<div class="kolecko">
</div>
<img src="css/img/logo.png" class="logo">
</div>
<div class="container">
<div class="slider">
<div class="slide">
<p>MB A35 AMG 2019 AeroPacket <br><span>Můžeš mě mít již od 4999 Kč</span><br>Pronajmout</p>
</div>
<div class="slide">
<p>Audi A7 V6T 2017 <br><span>Můžeš mě mít již od 4999 Kč</span><br>Pronajmout</p>
</div>
<div class="slide">
<p>Audi A3 2017 <br><span>Můžeš mě mít již od 4999 Kč</span><br>Pronajmout</p>
</div>
</div>
<div class="prolog">
<h1>Overcars s.r.o. - Půjčovna a prodejna luxusních automobilů</h1>
<p>Jsme malá začínající firma se zaměřením na pronájem a prodej vozů. Půjčujeme od levných vozů až po vozy luxusní! Naše vozy jsou s pravidelným servisem a ve 100% stavu. Řídíme se motem náš zákazník náš pán. Dokážeme zprostředkovat pronájem i prodej vozidel na míru.</p>
</div>
<div class="newslatters">
<h2>Chceš vědět, co se u nás děje?</h2>
<p>Přihlaš se k odběru novinek!</p>
<form action="#">
<input type="email" placeholder="Email" class="email">
<input type="submit" value="Odebírat" class="submit">
</form>
</div>
</div>
<footer>
<div class="author">
<p>Build with <i class="fas fa-heart"></i> by GMWebs</p>
</div>
</footer>
Can somebody help me please?
Thank you in advance for the advice!

Answer 1

It is definitely an issue with z-index.
You can simply add this CSS to your nav:
position: relative;
z-index: 1;
And remove the z-index: -1 from the .slider element.