Correct Login feature development for a website

I'm still new in web development and I am trying to develop a website to provide my local community with a practitioner directory with option of booking.

I want to get an opinion or recommendation from you experts whether the logic for my login functionality is correct.

Before I ask any question on this platform, please note that I have done extensive research and trials on web development.

Let me just explain the logic I implemented point wise.

1. Call DB Connection file
2. Start a new session
3. Unset variables (To start a fresh login)
4. Destroy open sessions
5. Make a new DB Connection
6. Read username and password input in form using POST method
7. Implement logic for login and display error messages (Check if user account is verified, check username and password)
8. Direct user to the next page once username and password is validated

// File that contains Database Connection details
require_once("dblogin.php");

// Initialize the session.
session_start();

// Unset all of the session variables.
$_SESSION = array();

// If it's desired to kill the session once you logout, also delete the session cookie.
// Note: This will destroy the session, and not just the session data!
if (ini_get("session.use_cookies")) {
    $params = session_get_cookie_params();
    setcookie(session_name(), '', time() - 42000,
        $params["path"], $params["domain"],
        $params["secure"], $params["httponly"]
    );
}

// Finally, destroy the session.
session_destroy();

// Connect to the database
$conn = new mysqli($servername, $username, $password, $dbname);

// Connection error to database
if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
}

if($_SERVER["REQUEST_METHOD"] == "POST") {

  // Initialize the session.
  session_start();

  // Get email from input form
  $email = mysqli_real_escape_string($conn, $_POST['email']);
  // Get password from input form and encrpy it
  $password = password_hash(mysqli_real_escape_string($conn, $_POST['password']),PASSWORD_BCRYPT);

  // Retrieve password from database for check
  $user_check_query = "SELECT * FROM user_account WHERE username='$email' LIMIT 1";
  $result = mysqli_query($conn, $user_check_query);
  $user = mysqli_fetch_assoc($result);

    // Checks if account is not verified
    if ($user['username'] === $email && password_verify($_POST['password'],$user[password]) && $user['account_verified'] === '0'){
        $error = "Your Account is not verified";
    // Checks if account is verified for normal user        
    }else if ($user['username'] === $email && password_verify($_POST['password'],$user[password]) && $user['user_type'] === "user" && $user['account_verified'] === '1') { 
            // Stores username as a variable
            $_SESSION['username'] = $user['username'];
            // Directs to index.php page
            header('location: index.php');
    // Checks if account is verified for doctor
    }else if($user['username'] === $email && password_verify($_POST['password'],$user[password]) && $user['user_type'] === "doctor" && $user['account_verified'] === '1'){
            // Stores username as a variable
            $_SESSION['username'] = $user['username'];
            // Directs to doctor profile page
            header('location: docbookings.php?docid='.$user['doctor_profile_id']);      
    }else {
         // If does meet above conditions, display invalid email or password
         $error = "Your Email Address or Password is invalid";
      }  
}

My expectations from this platform is not get someone code for me but to get an advice or recommendation on my logic so that the final product works fine.