My smart buttons script like that:
<script>
        paypal.Buttons({
            style: {
                layout:  'vertical',
                color:   'black',
                shape:   'rect',
                label:   'paypal',
                tagline: false,
                size: 'responsive',
            },

            createOrder: function() {


// Now return the `token` to the client
                var SETEC_URL = '/api/create-payment';
                var checkBox = document.getElementById("ship_to_different");
                var note = $("#ordernote").val();
                if (checkBox.checked == true){
                    var body = $("#checkoutt, #data").serializeArray();
                }else{
                    $('input[name=note]').val(note);
                    var body = $("#data").serializeArray();

                }
                $("#wait").show();
                return fetch(SETEC_URL, {
                    method: 'post',
                    headers: {
                        'content-type': 'application/json'
                    },
                    body: JSON.stringify({
                        body:body
                    })

                }).then(function (res) {
                    return res.json();
                }).then(function (data) {
                    return data.id;
                });


            },
            commit: false,
            onApprove: function(data) {

                var EXECUTE_URL = '/api/execute-payment';
                return fetch(EXECUTE_URL, {
                    method: 'post',
                    headers: {
                        'content-type': 'application/json'
                    },
                    body: JSON.stringify({
                        paymentID: data.paymentID,
                        payerID:   data.payerID,

                    })
                }).then(function(response) {
                    console.log(response);

                    if(response.statusText == 'OK'){
                        var checkBox = document.getElementById("ship_to_different");
                        var note = $("#ordernote").val();
                        if (checkBox.checked == true){
                            var xdata = $("#checkoutt, #data").serialize();
                        }else{
                            $('input[name=note]').val(note);
                            var xdata = $("#data").serialize();
                        }
                        $.ajax({
                            type:'post',
                            url:'check-data',
                            data:xdata,
                            success:function () {
                                $("#wait").hide();
                                $("#success").show();
                            },
                            error:function(request){
                                json = $.parseJSON(request.responseText);
                                $.each(json.errors, function(key, value){
                                    $('#error'+key).html('');
                                    $('#error'+key).append('<p class="erro">'+value+'</p>');
                                });
                            }
                        });

                    }
              })
            }, onError: function (err) {
                console.log(err);
            }
        }).render('#paypal-button-container');
    </script>
And server side

Create-Payment 
public function createorder(Request $request){

 $body = json_decode(json_encode($request['body']),true);

 foreach($body as $valpay){
 if($valpay['name'] == '_token'){
 unset($valpay);
 }elseif($valpay['name'] == 'title[]'){
 $titlepay[] = $valpay['value'];
 }elseif($valpay['name'] == 'product_id[]'){
 $product_idpay[] = $valpay['value'];
 }elseif($valpay['name'] == 'price[]'){
 $pricepay[] = $valpay['value'];
 }elseif($valpay['name'] == 'quantity[]'){
 $quantitypay[] = $valpay['value'];
 }elseif($valpay['name'] == 'ssh'){
 $shippingpay = $valpay['value'];
 }elseif($valpay['name'] == 'total'){
 $totalpay = $valpay['value'];
 }elseif($valpay['name'] == 'subtotal'){
 $subtotalpay = $valpay['value'];
 }elseif($valpay['name'] == 'tax'){
 $taxpay = $valpay['value'];
 }elseif($valpay['name'] == 'city'){
 $city = $valpay['value'];
 }elseif($valpay['name'] == 'country'){
 $country = $valpay['value'];
 }elseif($valpay['name'] == 'state'){
 $state = $valpay['value'];
 }elseif($valpay['name'] == 'street'){
 $street = $valpay['value'];
 }elseif($valpay['name'] == 'zip'){
 $zip = $valpay['value'];
 }elseif($valpay['name'] == 'coupon'){
 $coupon = $valpay['value'];
 }elseif($valpay['name'] == 'discount'){
 $discount = $valpay['value'];
 }elseif($valpay['name'] == 'data'){
 $data = $valpay['value'];
 }elseif($valpay['name'] == 'x1'){
 $gift = $valpay['value'];
 }elseif($valpay['name'] == 'cost'){
 $cost = $valpay['value'];
 }

 }
 $apiContext = new ApiContext(
 new OAuthTokenCredential(
 'clientID',
 'ClientSecret'
 ));
 $payer = new Payer();
 $payer->setPaymentMethod("paypal");


 if(isset($gift)){
 $item = new Item();
 $item->setName('Gift Coupon')
 ->setCurrency('USD')
 ->setQuantity('1')
 ->setPrice($cost);
 $items[] = $item;
 $subtotalpay = $cost;
 $totalpay = $cost;
 }else{
 foreach ($product_idpay as $key => $p_id){
 $item[$key] = new Item();
 $item[$key]->setName($titlepay[$key])
 ->setCurrency('USD')
 ->setQuantity($quantitypay[$key])
 ->setSku("123123") // Similar to `item_number` in Classic API
 ->setPrice($pricepay[$key]);
 $items[] = $item[$key];
 }
 }


 if(isset($coupon)){

 $subtotalpay = $coupon;
 $item[$key+1] = new Item();
 $item[$key+1]->setName('Coupon')
 ->setCurrency('USD')
 ->setQuantity("1")
 ->setSku("test") // Similar to `item_number` in Classic API
 ->setPrice('-'.$discount);
 $items[] = $item[$key+1];
 }

 if($taxpay == '1'){
 $tax = round($subtotalpay * 8.625/100,2);

 }else{
 $tax = 0;
 }
 $itemList = new ItemList();
 $itemList->setItems($items);


 $details = new Details();
 $details->setShipping($shippingpay)
 ->setTax($tax)
 ->setSubtotal($subtotalpay);

 $amount = new Amount();
 $amount->setCurrency("USD")
 ->setTotal($totalpay)
 ->setDetails($details);

 $transaction = new Transaction();
 $transaction->setAmount($amount)
 ->setItemList($itemList)
 ->setDescription("Payment description")
 ->setInvoiceNumber(uniqid());

 $redirectUrls = new RedirectUrls();
 $redirectUrls->setReturnUrl("http://homee.test/checkout")
 ->setCancelUrl("http://homee.test/checkout");

 $inputFields = new InputFields();
 $inputFields->setNoShipping(1);

 $webProfile = new WebProfile();
 $webProfile->setName('test'. uniqid())->setInputFields($inputFields);
 $webProfileId = $webProfile->create($apiContext)->getId();
 $payment = new Payment();
 $payment->setExperienceProfileId($webProfileId);
 $payment->setIntent("sale")
 ->setPayer($payer)
 ->setRedirectUrls($redirectUrls)
 ->setTransactions(array($transaction));

 $request = clone $payment;

 try {
 $payment->create($apiContext);
 } catch (PayPalConnectionException $ex) {
 echo $ex->getCode(); // Prints the Error Code
 echo $ex->getData(); // Prints the detailed error message
 die($ex);
 } catch (Exception $ex) {
 die($ex);
 }

 $approvalUrl = $payment->getApprovalLink();



 return $payment;
}