pos page to be more easier with ajax , js

i have a page from a project
project built by asp.net c#
i need someone to complete the work and make it easier
-get a category from db
-get product under the category
-and the selected product to invoice cart
-calculate the total
-save the info to the db
*DB is done , most of the classes is done

for more information contact to DM

Note: unreasonable prices will be rejected