Sync Shopify with another b2b ecommerce

Hello,
my supplier has created b2b portal and api, i need to sync all with him.

The following services/endpoints are available:

Authenticate
/dealers/authenticate
This will create an authorization token that is required for subsequent calls to one of the other endpoints
GetPartInfo
/dealers/part
This will retrieve information on certain partnumber. Info like Description, Manufacturer, Price, Stock etc
GetPartInfoById
/dealers/part/{PartId}
Retrieves part info based on part id.
GetParts
/dealers/all-parts
This will retrieve all information for all parts that a customer has access to at once
GetMultiplePartInfos
/dealers/parts
Retrieves part info for multiple parts
PostNewOrder
/dealers/order
Places a new order with the specified items.
GetOrderTracking
/dealers/order/tracking
Retrieves tracking numbers based on order number.
GetShipment
/dealers/shipment/{ShipmentId}
Get details of a specific shipment
GetShipments
/dealers/shipments
Get all shipments between a start and end date