How to give access to my facebook catalog to an other WhatsApp business to post it in chat manualy

I have a catalog that I have created using Facebook System user, and Graph API. I want to give access to my catalog to an other user. So that the other user is able to use the items from this catalog in its WhatsApp Business app, and to post the products from that catalog in his WhatsApp business chat.

The Graph API is really hard to understand, because there are many types of ids and tokens. It is very hard to understand what id should be used. Sometimes they use “business_id” sometimes they use just “business” and this is just small thing of all wrong things. Some of the edges don’t work at all. The errors that their API returns are misleading and unclear. So I spend a lot of time trying to understand how the things are connected, and when I thought I understand it, I came to this task and this question.

So what I managed to achieve is

Created catalog via the API system user
Creating a product in it
Manually added the business ID of the other user to the catalog
Manually the other user used the WhatsApp manager and connected WhatsApp configuration created in his facebook app (meta for devs apps). After that using the WhatsApp manager he added the catalog as catalog for the WhatsApp.

And here I am. The catalog he connected is not accessible from the WhatsApp menu on his mobile device (WhatsApp for business). And when he tried to create catalog from the mobile app, the mobile app created completely different catalog. (It looks like the WhatsApp business app cannot work with the catalog assigned from Meta Business Suite)

The idea on my side is to be able to give automatic access to my catalog to this user. Why? Because I have many other catalogs for which I want to give access automatically to other WhatsApp business users. But I don’t even understand how the things would work manually. Asking this question I hope that someone can give me some flow that could work for solving this task.