HTML JAVASCRIPT providing links between different html files

This code in adminPage.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Admin Page</title>
    <style>
        body {
            margin: 0;
            padding: 0;
            font-family: Arial, sans-serif;
        }

        nav {
            background-color: #333;
            overflow: hidden;
        }

        nav ul {
            list-style-type: none;
            margin: 0;
            padding: 0;
            overflow: hidden;
        }

        nav ul li {
            float: left;
        }

        nav ul li a {
            display: block;
            color: white;
            text-align: center;
            padding: 15px; /* Küçültüldü */
            text-decoration: none;
        }

        nav ul li a:hover {
            background-color: #555;
        }

        .page {
            display: none;
            padding: 20px;
        }

    </style>
</head>
<body>
<nav>
    <ul>
        <li><a href="#" onclick="showDoctorPage()">Doktor İşlemleri</a></li>
        <li><a href="#" onclick="showHastaPage()">Hasta İşlemleri</a></li>
        <li><a href="#">Rapor İşlemleri</a></li>
    </ul>
</nav>

<div id="doctorPage" style="display: none;">

</div>
<div id="hastaPage" style="display: none;">

</div>

<script>

    function showDoctorPage() {
        // Doktor sayfasını göstermek için işlevi uygula
    }


   function showHastaPage() {
    var xhttp = new XMLHttpRequest();
    xhttp.onreadystatechange = function() {
        if (this.readyState == 4 && this.status == 200) {
            document.getElementById("hastaPage").innerHTML = this.responseText;
        }
    };
    xhttp.open("GET", "/admin/page/patients", true); // /admin/page/patients endpoint'ine GET isteği yapılıyor
    xhttp.send();
}

</script>



</body>
</html>

This code in patientOp.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>{%  block title  %}Hasta İşlemleri{% endblock %}</title>
    <style>
        .add-form {
            display: none;
            margin-top: 20px;
        }

        form label {
            display: block;
            margin-bottom: 5px;
        }

        form input {
            width: calc(25% - 7px); /* Genişlik küçültüldü */
            padding: 8px;
            margin-bottom: 10px;
            margin-top: 10px; /* Yukarı kaydırma */
            border: 1px solid #ccc;
            border-radius: 4px;
            box-sizing: border-box;
        }

        form button {
            padding: 8px 16px; /* Küçültüldü */
            border: none;
            border-radius: 4px;
            cursor: pointer;
        }

        button.delete-button {
            background-color: #d42f2f;
            border: none;
            color: white;
            padding: 7px 12px;
            text-align: center;
            text-decoration: none;
            display: inline-block;
            font-size: 16px;
        }

        button.add-button {
            background-color: #04AA6D; /* Green */
            border: none;
            color: white;
            padding: 7px 12px;
            text-align: center;
            text-decoration: none;
            display: inline-block;
            font-size: 16px;
            /* İstediğiniz miktarı ayarlayın */
        }

        button.save-button {
            background-color: #669ee7;
            border: none;
            color: white;
            padding: 7px 12px;
            text-align: center;
            text-decoration: none;
            display: inline-block;
            font-size: 16px;
        }

        button.edit-button {
            background-color: #ccf627; /* Green */
            border: none;
            color: white;
            padding: 7px 12px;
            text-align: center;
            text-decoration: none;
            display: inline-block;
            font-size: 16px;
        }

        button:hover {
            opacity: 0.8;
        }

        table {
            width: 70%;
            border-collapse: collapse;
            margin: 0;
        }

        table th, table td {
            padding: 6px; /* Küçültüldü */
            border-bottom: 1px solid #ddd;
            text-align: left;
        }

        table th {
            background-color: #464a47;
            color: rgb(255, 255, 255);
        }
    </style>
</head>
<body>
<h1>{% block header %}Hasta İşlemleri{% endblock %}</h1>

{% block content %}
<h1>Hasta Ekle</h1>
<button class="add-button" onclick="showAddHastaForm()">Hasta Ekle</button>
<div id="addHastaForm" class="add-form" style="display: none;">
    <form id="hastaForm" action="{{ url_for('admin_patient_page') }}" method="POST">
        <label for="username">Kullanıcı Adı:</label>
        <input type="text" id="username" name="patient_username"><br>
        <label for="password">Şifre:</label>
        <input type="password" id="password" name="patient_password"><br>
        <label for="firstName">Ad:</label>
        <input type="text" id="firstName" name="patient_name"><br>
        <label for="lastName">Soyad:</label>
        <input type="text" id="lastName" name="patient_surname"><br>
        <label for="birthday">Doğum Tarihi:</label>
        <input type="text" id="birthday" name="patient_birth_date"><br>
        <label for="gender">Cinsiyet:</label>
        <input type="text" id="gender" name="patient_gender"><br>
        <label for="adres">Adres:</label>
        <input type="text" id="adres" name="patient_address"><br>
        <label for="telephone">Tel No:</label>
        <input type="text" id="telephone" name="patient_phone"><br>
        <button type="submit" class="save-button">Kaydet</button>
    </form>
</div>
<div id="hastaList">
    <h2>Eklenen Hastalar</h2>
    <table id="hastalar">
        <thead>
        <tr>
            <th>Kullanıcı Adı</th>
            <th>Şifre</th>
            <th>Ad</th>
            <th>Soyad</th>
            <th>Doğum Tarihi</th>
            <th>Cinsiyet</th>
            <th>Adres</th>
            <th>Tel No</th>
            <th>İşlemler</th>
        </tr>
        </thead>
        <tbody>
        {% for patient in patients %}
        <tr>
            <td>{{ patient.patient_username }}</td>
            <td>{{ patient.patient_password }}</td>
            <td>{{ patient.patient_name }}</td>
            <td>{{ patient.patient_surname }}</td>
            <td>{{ patient.patient_birth_date }}</td>
            <td>{{ patient.patient_gender }}</td>
            <td>{{ patient.patient_address }}</td>
            <td>{{ patient.patient_phone }}</td>
            <td>
                <button class="edit-button" onclick="editHasta(this)">Düzenle</button>
                <form action="{{ url_for('delete_patient', patient_id=patient.patient_id) }}" method="POST" style="display: inline;">
                    <button type="submit" class="delete-button">Sil</button>
                </form>
            </td>
        </tr>
        {% endfor %}
        </tbody>
    </table>
</div>

{% endblock %}
<script>
    function showAddHastaForm() {
        var addHastaForm = document.getElementById('addHastaForm');
        addHastaForm.style.display = 'block';

        // Formun içindeki inputları temizle
        var inputs = addHastaForm.querySelectorAll('input');
        inputs.forEach(input => {
            input.value = '';
        });
    }

    function editHasta(button) {
        var row = button.parentNode.parentNode;
        var cells = row.getElementsByTagName('td');
        var username = cells[0].textContent;
        var password = cells[1].textContent;
        var firstName = cells[2].textContent;
        var lastName = cells[3].textContent;
        var birthday = cells[4].textContent;
        var gender = cells[5].textContent;
        var adres = cells[6].textContent;
        var telephone = cells[7].textContent;

        document.getElementById('username').value = username;
        document.getElementById('password').value = password;
        document.getElementById('firstName').value = firstName;
        document.getElementById('lastName').value = lastName;
        document.getElementById('birthday').value = birthday;
        document.getElementById('gender').value = gender;
        document.getElementById('adres').value = adres;
        document.getElementById('telephone').value = telephone;

        row.parentNode.removeChild(row);
    }
</script>

</body>
</html>

I can’t make a connection between two different codes here.

First of all, when I click on ‘Patient Operations’ in the adminPage, I want the interface in patientOp.html to appear. However, this interface must go directly under the bar. Additionally, they both need to be in different HTML files. How can I do that?