Updating Product Features Via Nsurl (Swift)

I want to create a new product with features via the API. I have created the request on Postman and it works ok there as well as the cURL code that Postman produces.
However, when I try to run the equivalent code from a playground or project in Swift (iOS) everything is created except the product features. I am guessing that this is because it is a nested array.
Does anyone have any previous experience on that?
This can be easily tested it if you create the call in Postman, then copy/paste the Swift(NSURL) snippet code and run it in XCode.

I just found out that if you don't set the language as the same language as you are viewing the product on the admin panel , the product options will not show... that was it...

thx for solution