Not able to send auto emails from my hotel booking payment gateway plugins

The payment gateway setup are done with WP hotel booking & Woo Commerce plugins for payumoney using php & WP. I am able to search room and make payment from cart. The payment is coming to my account. But, after deducting amount from customer account somehow site is not able to send emails to customer & owner. Hence system is giving errors 1) " Fatal error:cannot redeclare class phpmailerexception in /home/aquamarinapark/public_html_wp-includes/[login to view URL] on line 4040".If I cancel the payment from payment portal then I am getting error " Call to a member function get_sku() on a non-object in /home/......./public/wp-content/plugins/woocommerce/templates/emails/plain/[login to view URL] on line 27". In both the cases, as the order is showing completed in woo commerce order table but the same transaction remaining pending in the booking table of wp hotel booking plugin. Also I am getting a memory exhausted error so need to increate allocated memory size putting config file for my host account. So, would like to correct/ remove all the errors and the functionality should work perfectly without any issue. If there is any further issue occurred that also has to fix as part of this project. Hint & Note: was used default email address during WP latest version installed and the different email is used in plugin configuration. I hope you catch the point of causing the issue for the necessary troubleshoot