Active CMS modification and features addition

I've active e-commerce cms and looking for an expert to modify on it.

Working on the affiliate program for the ecommerce/cms part.
Cupon system integration and configuration for the merchants and admins.
Promocode generation, integration, calculation and reporting as per the CMS features
Affiliate sales leads generation and maintaining in the cms or associated database files
React native APP :
open a field( Promocode in checkout) or box to fill the coupons and let user apply it
Flutter APP:
nothing to devlope ; just just checking the same field ( Promocode in checkout) working and report to the target system