PayPal Plus stay on own page - asp.net

Question

I have implemented a small PayPal PLUS Demo in ASP.NET:
protected void Page_Load(object sender, EventArgs e)
{
var config = ConfigManager.Instance.GetProperties();
config.Add("clientId", "XXXXXXXXXXXXXXXXXXXXXXXXX");
config.Add("clientSecret", "XXXXXXXXXXXXXXXXXXXXXXXXX");
config.Add("mode", "sandbox");
var accessToken = new OAuthTokenCredential(config).GetAccessToken();
var apiContext = new APIContext(accessToken);
var itemList = new ItemList() { items = new List<Item>() { new Item() { name = "Item Name", currency = "USD", price = "15", quantity = "5", sku = "sku" } } };
var payer = new Payer() { payment_method = "paypal" };
var baseURI = Request.Url.Scheme + "://" + Request.Url.Authority + "/PaymentWithPayPal.aspx?";
var guid = Convert.ToString((new Random()).Next(100000));
var redirectUrl = baseURI + "guid=" + guid;
var redirUrls = new RedirectUrls() { cancel_url = redirectUrl + "&cancel=true", return_url = redirectUrl };
var details = new Details() { tax = "15", shipping = "10", subtotal = "75" };
var amount = new Amount() { currency = "USD", total = "100.00", details = details };
var transactionList = new List<Transaction> { new Transaction() { description = "Transaction description.", invoice_number = new Random().Next(999999).ToString(), amount = amount, item_list = itemList } };
var payment = new Payment() { intent = "sale", payer = payer, transactions = transactionList, redirect_urls = redirUrls };
var createdPayment = payment.Create(apiContext);
var approval_url = createdPayment.links.FirstOrDefault(x => x.rel == "approval_url").href;
hfApprovalUrl.Value = approval_url;
}
<asp:HiddenField runat="server" id="hfApprovalUrl"/>
<script src="https://www.paypalobjects.com/webstatic/ppplus/ppplus.min.js" type="text/javascript"></script>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>
<div id="ppplus"></div>
<script type="application/javascript">
var approval_url = $('#hfApprovalUrl').val();
var ppp = PAYPAL.apps.PPP({
"approvalUrl": approval_url,
"placeholder": "ppplus",
"mode": "sandbox",
"country": "DE"
});
</script>
Its works so far but if a choose a pay option (e.g. credit card) I will be redirected to PayPal.I want that the user stys on my own page. How can I do this?
Thanks!
Jan