I'm not entirely sure what your data looks like, but from our API you can include the properties that you want in the response for each contact. It's documented in the URL I included above, but you can include &property= in the query string of your request URL. So for example: https://api.hubapi.com/contacts/v1/lists/all/contacts/all?hapikey=XXXX&property=email&property=first... . That will include the values for those properties in the response for each object, assuming the contact record has values for those properties.
If you're still having trouble, just let me know how you're making the request and I'll be happy to look again.