Parse Json String Without using newtonsoft

Question

I encountered an issue which is I want to get the data from innermost json. Eg, I input Swimming then I will get student_ID : 0001 and Name : Jack. Something like this but I don't want to use Newtonsoft or any other dll. My current code is shown below, I able to get data for the outmost which is Name and Birthday but not embedded. My code and json are below

{
   "Name":"Jack",
   "birthday":"11-Jan-2022",
   "embedded":{
      "OtherInfo":[
         {
            "student_ID":"0001",
            "Batch":"2022-02",
            "Hobby":{
               "Sport":"Swimming",
               "Arcade":"Fencing"
            }
         }
      ]
   }
}

    public class Hobby
    {
        public string Sport { get; set; }
        public string Arcade { get; set; }
    }

    public class OtherInfo
    {
        public string student_ID { get; set; }
        public string Batch { get; set; }
        public Hobby Hobby { get; set; }
    }

    public class Embedded
    {
        public List<OtherInfo> OtherInfo { get; set; }
    }

    public class Root
    {
        public string Name { get; set; }
        public string birthday { get; set; }
        public Embedded embedded { get; set; }
    }

var jsonObj = new JavaScriptSerializer().Deserialize<Root>(ApiCreateJsonData);
string testtsett = "";
foreach (var item in jsonObj.Name)
{
    testtsett += item.ToString();   
}
Label1.Text = testtsett;