Magento – How to get an order id in success.phtml block

I understood my problem it was in config.xml, I changed class like this:

 <core_block_abstract_to_html_before>
                <observers>
                    <cart_shopping>
                        <type>model</type>
                        <class>Cart_Shopping_Model_Observer</class>
                        <method>insertBlock</method>
                    </cart_shopping>
                </observers>
            </core_block_abstract_to_html_before>

and also I did what Amit said about the template

you can call your helper function as per below,

 namespace Vendor\Module_Name\Block\Product;
     class ListProduct extends \Magento\Catalog\Block\Product\ListProduct
     {
           public function __construct(
            \Magento\Catalog\Block\Product\Context $context,        
            \Magento\Framework\Data\Helper\PostHelper $postDataHelper,
            \Magento\Catalog\Model\Layer\Resolver $layerResolver,
            \Magento\Catalog\Api\CategoryRepositoryInterface $categoryRepository,
            \Magento\Framework\Url\Helper\Data $urlHelper,
            \Vendor\Mymodule\Helper\Data $dataHelper,
            array $data = []
        ) {
            $this->dataHelper = $dataHelper;       
            parent::__construct(
                $context,
                $postDataHelper,
                $layerResolver,
                $categoryRepository,
                $urlHelper,
                $data
            );
        }

       public function test(){
            $this->dataHelper->getHelperFunction();
       }
    }

Remove var folder and refresh again.