If you like personal help please contact me by clicking on my website under my name and go to contact and I am happy to provide you with personal help.
To create content API, you need to learn the Shopify API, and yes you can pull that data using REST or GraphQL, then create a Content API setup.
However I'm guessing you are more interested in a rebuild app: https://apps.shopify.com/multiple-google-shopping-feeds
my google merchant account is suspended due to "currency", however after contacting google, they are claiming the following:Please be advised that as the input method you are using is content API, remove the item ID from the Content API.Please find the below example for your reference:
Title: Gift Card $95.00
Item ID: shopify_US_4613598838869_32101614551125If you have any queries related to Content API, please contact Content API team as Content API is out of my purview. I hope you understand our limitations.
You can ask questions for Google Content API on the official community here: https://groups.google.com/forum/#!forum/google-content-api-for-shopping
Content API doesn't enable to replicate items for multiple countries within a single feed. If you want to submit your Content API product data to multiple countries, you'll need to upload the product multiple times, once for each targeted country-language pair through the API. Here, you will find more info about it.
If you want to save time, this Google ads and Shopify app do the work for you. Using an app like this one will help you to advertise your Google Shopping campaigns across multiple countries. It will create, manage and automate your Merchant Center or Google Shopping campaigns.