bug shop: derived from oscommerce - at the first entry the cart is emptied, paypal random does not close the order, export data on existing feed

I have a customized ecommerce derived from oscommerce, working but with problems : 1 - problem sometimes at the first entry the customer puts a product in the cart but the cart is empty,immediately or just after entering the data as a guest purchase. 2 - problem maybe it is connected to the first one, paypal advance works but sometimes the money arrives, the order is not closed it remains hanging or deleted. 3 - I have to add 2 data fields in the present order export feed the main product image link and invoice yes or no, data to be taken from the database in the relative tables