Need to fix issues of the project Grupojk.co.uk

This is an wholesale E-commerce website where below issues are present : There are 4 types of discount working over the project - need to write condition when the highest amount of discount applies over the cart when all discounts are given - currently it is not working properly E-mails should go to customer when they do registration, purchase products, when their order is paid, order delivered, order dispatched etc. currently emails are not working properly There is a supplier module over the website on which quantity delivered by the supplier are coming incorrect in the mail, need to fix that