How do I desiralize the webhooks binary text?

I am using photon-webhook v1.2 with Azure.
As shown in the following example,
I'm trying to decode base64, but I'm asking because it didn't go well.
====================================================
Azure function app
[ input ]
------------------------------------------------------------------------------------------------
"Binary":{"18":"RAAAAAVzAAhHYW1lRmxvd2kAAAABcwADcmR2aR7qYwti+nkAAnMAAkMwAAJDMXMAAkMwaQAAAZBzAAJDMXMABE1hcDM="}
------------------------------------------------------------------------------------------------
[ example code ]
public class MyClass
{
public int GameFlow;
public long rdv;
}
public static T FromBase64<T>(string data)
{
var base64EncodedBytes = Convert.FromBase64String(data);
string parsedString = Encoding.UTF8.GetString(base64EncodedBytes);
return JsonConvert.DeserializeObject<T>(parsedString); // what should I do ?
}
string byText = gdRequest.State.Binary["18"];
MyClass myClass = FromBase64<MyClass>(byText);
Thank you in advance.