Build sales and payment settlement functionalities in Django

I have a website in which I have few bugs to fix and few new functionality implementations to do. The frameworks and languages used are: HTML, CSS, Jquery, AJAX, Django, MySQL Things to be done are: - Add the sales details (already built and minor changes required) - Payment settlement where we will have around 10-15 items which can be edited - We can select any number of the sales rows to process the payment for - Generate payment advice and Tax invoice and send in email as attachment - Minor calculations Remember one thing that the MySQL database is taken from our old website which was earlier built on PHP. So there are so many django inbuilt functions and other stuffs not being used or cannot be used in our application. So bid only if you can handle this.