Backend developer, experienced in building API's and customer account environments

For several projects, I need a backend developer. Examples of projects:
We are building a shopify website for a B2B customer, in which customers needs to get the ability to login in their account and they can check products for which prices and discounts apply specific for this customers account. We need to have the ability to set this easily per customer and connect this through an API to our Administration system (business central).

Another project is:
We build a new Shopify website, in which we can extract the articles from a server of our supplier. The API-data is available and I think it is quite easy, ,but we need to get the ability to build an API to extract up-to-date article data out of the suppliers system.

And more projects will definitely follow, so I am willing to hire you (if it fits the expectations) for the longer term.