Plugin to save data from external API to database

Hello everyone,

I’m making an app which relies on getting information about a shop’s products from shopify (external api). Unfortunately, the api sends data with this structure:

Array of rows (with each row having an array of products) and each product having multiple fields.
(Picture of the received data format attached below, if its not clear)
Hence the data is sent as sort of a list within a list. Can anyone guide me on how to best approach writing a plugin that both calls the extrenal API and then saves all of the products to a database? (I tried doing this without a plugin but to no avail)

Would really appreciate some guidance as I’m a beginner to plugin development.