C# Update Game & Title forbidden

API
3

I’m fairly new to C# so… can you explain how I do that?
I tried it using this command:
var body = response.Content.ReadAsStringAsync().Result;
Console.WriteLine(body);

But the response is

????D?K
?0D?"?."??x?@?6~@-??J???*.g^?,?-:’?b-?P???6U???f?tr?K(#?X??,k\ab?K?????a>????????e?P???

The commands var body = response.Content.ReadAsStringAsync(); and var body = response.Content; doesn’t tell me anything interesting.