Modify json result and send it back, VBA

I have a result from an API and the way this API work, to modify even only one field, I have to send back all fields.
What I whant is to modify the fields I whant and send back the info to the API.
I know I can use string function to do that, but I whant to know if theres a library or sommething more simple that I can use to just change some part of the result.
Here what I receive from the API:

{
  "id": "a05b0aa4-d622-4bda-8a0d-0b287bc43c7a",
  "idStatus": null,
  "isUser": false,
  "company": null,
  "department": null,
  "companyID": "",
  "contactType": "Contact",
  "firstName": "test302",
  "lastName": "test2",
  "lastResults": null,
  "messengerID": null,
  "middleName": null,
  "nameSuffix": null,
  "namePrefix": null,
  "fullName": "test302 test2",
  "referredBy": null,
  "salutation": "test302",
  "jobTitle": null,
  "emailAddress": "dfgfdg£g.com",
  }

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I need to send back the exact same thing but with some change. Exemple, I would like to change the "firstname" to something else.