<?php

if ( 1 > count( $reg_errors->get_error_messages() ) ) {
    $userdata = array(
        'user_login' => $useremail,
        'user_email' => $useremail,
        'user_pass'  => $password,
        'role'       => 'Arbeitnehmer'
    );
    $user     = wp_insert_user( $userdata );
    echo "Erfolgreich registriert!";
}

<form method="post" action="<?php echo get_template_directory_uri() ?>/register_handler/register_normal_user.php"  id="registrieren-form">
                <div class="row boxes">
                    <!--<label for="email">E-Mail</label>-->
                    <input type="text" name="email" id="email" placeholder="E-MAIL">
                    <!--<label for="password">Passwort</label>-->
                    <input type="password" name="password" id="password" placeholder="PASSWORT">
                    <!--<label for="password_check">Passwort wiederholen</label>-->
                    <input type="password" name="password_check" id="password_check" placeholder="Passwort wiederholen">
                </div>
                <div class="row terms" >
                    <label for="terms"><?php echo $registerbox['terms']; ?></label>
                    <input name="terms" id="terms" type="checkbox" value="Yes">
                </div>
                <div class="row">

                    <input type="submit" id="signin" name="submit" value="Registieren"/>

                </div>

            </form>