Como por caixa de texto lado a lado css html

Boas. Gostaria de saber como e que eu posso por um registar e um login lado a lado usando o css ou ate mesmo no html se possivel. aqui esta o meu codigo que interessa caso precisem.

<li class="nav-item"> \\menu registar e login que clicando me vai parar a outra parte da página
<a class="nav-link js-scroll-trigger" href="#signup">Register</a>
</li>
<li class="nav-item">
<a class="nav-link js-scroll-trigger" href="#signup">Login</a>
</li>
<form class="form-register form-inline d-flex" method="post" action="">
<input type="name" type="email" class="form-input form-control flex-fill mr-0 mr-sm-2 mb-3 mb-sm-0" id="inputName" placeholder="Username" name="name">
<input type="password" class="form-input form-control flex-fill mr-0 mr-sm-2 mb-3 mb-sm-0" id="inputPassword" placeholder="Password" name="password">

</form>





<form class="form-register form-inline d-flex" method="post" action="">
<input type="name" class="form-input form-control flex-fill mr-0 mr-sm-2 mb-3 mb-sm-0" id="inputName" placeholder="Username" name="name">
<input type="email" class="form-input form-control flex-fill mr-0 mr-sm-2 mb-3 mb-sm-0" id="inputEmail" placeholder="Email" name="email">
<input type="password" class="form-input form-control flex-fill mr-0 mr-sm-2 mb-3 mb-sm-0" id="inputPassword" placeholder="Password" name="password">
<input type="password" class="form-input form-control flex-fill mr-0 mr-sm-2 mb-3 mb-sm-0" id="inputPassword" placeholder=" Confirme a Password" name="*"> <button type="submit" class="btn btn-primary mx-auto">Registar</button>

</form>
<form class="form-login form-inline d-flex" method="post" action="">
<input type="name" class="form-input form-control flex-fill mr-0 mr-sm-2 mb-3 mb-sm-0" id="inputName" placeholder="Username" name="name">
<input type="password" class="form-input form-control flex-fill mr-0 mr-sm-2 mb-3 mb-sm-0" id="inputPassword" placeholder=" Password" name="*"> <button type="submit" class="btn btn-primary mx-auto">Login</button>

</form>