API, XML full integration with supplier on my Shopify website

I am building a Shopify e-commerce store where I will sell adult pleasure products online and dropship through my supplier. I am in need of an expert Shopify developer who is experienced with API and XML and can provide a full integration between my online store and the supplier’s data (through API) within 5 days of accepting the job. The expert must be able to show me (and teach me) how to use the API after its completion. Notice: I want this to be mine alone. I will not pay a monthly fee for access to the app. Here is information from the supplier about the API: • The API follows the REST specification and all calls are made using GET or POST requests to the specified endpoints. • All calls can be made by using cURL or the HTTP tools which come with any standard web programming language. For the purposes of the documentation, we will be showing calls made using cURL on the command line, but you can make the same calls using PHP, Java, Ruby, et cetera. • API response data can be returned in JSON or XML format by specifying "Content-Type: application/json" or "Content-Type: application/xml" in the header. If no content type is specified, the default format is JSON. For POST requests, the incoming content will be parsed depending on the Content-Type header, and also defaults to JSON. • I will supply my API key and email address when necessary. • They also have tabs for Product Data, List Orders, Create Orders with a bunch of code. Additionally, they use XML files to update inventory x2 per day, which I will need. I also want a way to add my price increase to their base price and have it calculate the asking price onto the website. I had previously used another developer, but I am unsure whether what he did is actually functional as i made a change with my supplier. Thank you, and I look forward to working with you!