Hello,
You said
As we downloaded W3 cache plugin it makes our website fast but our website starts misbehaving
Please clarify what exactly is wrong with your site when cache plugin is activated.
Concerning the search you may try to edit the file wp-content/themes/royal/woosearchform.php on line 15 and remove the code <input type="hidden" name="post_type" value="product" />
. In this case you’ll have default search form.
Regards,
Eva Kemp.