Yii2 rendering in a specific div - php

Question

I'm using Yii2-advanced-template. I've 2 divisions on my form as follows - When I'll click on any of the radio button in 2nd div, the details of respective entry should be loaded in 1st div. That is, the form in 1st div will remain as is, but loads some values for update operation. But I'm getting it as - which is not what I expect. It is loading the whole page layout in that div.
I already used 'renderPartial()' in my controller. But it solved only the half of the problem, that is, the navigation bar & other layout is hidden after using renderPartial().
My form is as follows-
<div class="col-sm-12">
<div class="col-sm-6 fillitemform">
...
Enter Item Details form
...
</div>
<div id="item_details" class="col-sm-6">
<div class="panel panel-primary">
<div class="panel-heading">
<h3 class="panel-title">Item details</h3>
</div>
<div class="panel-body">
<div class="table-responsive" >
<table class="table">
<thead>
<tr><th></th>
<th>PO No.</th>
<th>SKU</th>
<th>Order Type</th>
<th>Expected Qty</th>
<th>Received Qty</th>
<th>Weight</th>
</tr>
</thead>
<tbody>
<?php
for($itr = 0, $ro = $modelRO, $rod = $modelROD; $itr < count($modelROD); ++$itr){
echo '<tr onclick="placeitemdtls('.$rod[$itr]['id'].')">';
echo '<td><input type="radio" name="item"></td>';
echo '<td>'.$ro[0]['ro_po_no'].'</td>';
echo '<td>'.$rod[$itr]['rod_sku'].'</td>';
echo '<td>'.$ro[0]['ro_order_type_id'].'</td>';
echo '<td>'.$rod[$itr]['rod_expected_qty'].'</td>';
echo '<td>'.$rod[$itr]['rod_received_qty'].'</td>';
echo '<td>'.$rod[$itr]['rod_weight'].'</td>';
echo '</tr>';
}
?>
</tbody>
</table>
</div>
</div>
</div>
</div>
</div>
My JS/jQuery function-
function placeitemdtls(id){
$.post("index.php?r=receiving-order-details/update&id="+id, function(response) {
jQuery(".fillitemform").html(response);
});
}
My Controller function-
public function actionUpdate($id)
{
$model = $this->findModel($id);
$modelRO = ReceivingOrders::find()->where(['id' => $id])->all();
$modelROD = ReceivingOrderDetails::find()->where(['receiving_order_id' => $id])->all();
if ($model->load(Yii::$app->request->post()) && $model->save()) {
return $this->redirect(['create', 'id' => $id]);
} else {
return $this->renderPartial('update', [
'model' => $model, 'modelRO' => $modelRO, 'modelROD' => $modelROD,
]);
}
}
Please note that, I'm getting the correct form with proper values, but having rendering problem as I showed in 2nd image. Please help me to solve it. So that my output should look like -