Your problem is that you put a reference of data-target="#navbarNav"
different from the ID
you used in <div class="collapse navbar-collapse" id="navbarSupportedContent">
Note that putting the same value navbarNav
into ID
of div id="navbarNav"
into your Nav will work.
Follow the template. I did not change anything, I just set target
to the right ID.
<link rel="stylesheet" type="text/css" media="screen" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" />
<script src="https://code.jquery.com/jquery-3.2.1.min.js"></script><scriptsrc="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js"></script>
<header>
<nav class="navbar navbar-expand-lg navbar navbar-dark bg-dark">
<a class="navbar-brand" href="./TheStrangerFish.html"><img src="./logo.png" height="50" width="50" class="d-inline-block align-top"
alt=""> HARD PUNK </a>
<button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarNav" aria-controls="navbarN"
aria-expanded="false" aria-label="Toggle navigation">
<span class="navbar-toggler-icon"></span>
</button>
<div class="collapse navbar-collapse" id="navbarNav">
<ul class="navbar-nav mr-auto">
<li><a class="nav-link" href="#">Sobre o Jogo</a></li>
<li><a class="nav-link" href="#">Desenvolvedores</a></li>
<li><a class="nav-link" href="#">Contato</a></li>
</ul>
</div>
</nav>
</header>