dynamic stuff = JsonConvert.DeserializeObject("{ 'Name': 'Jon Smith', 'Address': { 'City': 'New York', 'State': 'NY' }, 'Age': 42 }");

string name = stuff.Name;
string address = stuff.Address.City;

https://stackoverflow.com/questions/3142495/deserialize-json-into-c-sharp-dynamic-object

Token

var data = pm.response.json();

pm.environment.set("Token", "Bearer "+ data.access_token);

Get header value from request

private string GetHeaderValue(string key)
{
    Request.Headers.TryGetValue(key, out var value);
    if (string.IsNullOrWhiteSpace(value))
        throw new ArgumentException($"Key missing: {key}");
    return value;
}