Need a QuickBooks Online API developer (C# .net core) to Integrate with our POS/ERP -- 2

Job ID: 38297271

Budget: $250 – $750 USD

We need a developer, not an accountant!!! and
ONLY WITH EXPERIENCE WITH QUICKBOOKS ONLINE

I need an expert in C# to integrate our Point of Sale/Enterprise Resource Planning (POS/ERP) system named "CIZARO" with QuickBooks Online. The goal is the seamless syncing of different modules,

We already have a similar code we made integration with SAP Business One for example how to do integration, We have coded someone to start integrating directly with QuickBooks Online.

we can share this code to have the fastest development, and we also have the code of a previous developer who made Quickbooks Online but it half done.

This Milestones we will have
Milestone 1: will be for 120 USD for Sync Products, categories, variants, discounts, pricelist dual CIZARO to QuickBooks Online and QuickBooks Online to CIZARO
Milestone 2: will be for 120 USD Send QuickBooks Online Orders and invoices with information on the Customer, sale order, sales order lines, payments, order statutes, and delivery info and to update inventory.
Milestone 3: will be for 120 USD Get inventory from QuickBooks Online and update in CIZARO to Change order status at QuickBooks Online from CIZARO order-status, and Refund order process,
(not include RMA (Return to reseller it will be in another project)

Experience with developing QuickBooks APIs and C# .net Core professional is imperative for this role. Experience with similar projects will be highly valued.