Ionic 2 nested http requests

Im making a business app that makes alot of api calls and most of them depends on each other.
For example in first api call I make from “(” I get a json file that contains groupids and with those ids I need to make a new request to collect the data.

I have tried out with forkJoin with static data and that works good, but now I first need to parse the JSON file and store the ids in a array and after that make a new requests with all those ids.
Any idea how to implement a working solution?
Sry for my english.