React JavaScript Work

Hi,
I am developing eCommerce website using JavaScript React, Node .
I am unable to fix 2 small part.
I want to fix 2 part Only. You can fix it within 30 Minutes.

I have attached an image screenshot. Please check

I want to fix:
1. If I click deliver Now Button Then 1 Quantity will minus from the product
2. If I add Quantity Then This Quantity will add with product Quantity.

Very easy work. I will send you all codes. You will fix and you will just send me that specific js files..

My Node Version: 14.17.6

Thanks