I obviously can't test it, but something like this:
static void Main(string[] args)
{
HttpClient c = new HttpClient();
c.DefaultRequestHeaders.Clear();
c.DefaultRequestHeaders.Add("content-type", "application/json");
c.DefaultRequestHeaders.Add("user-agent", "Mozilla/5.0 AppleWebKit/537.36 (KHTML, like Gecko) Chrome/86");
c.DefaultRequestHeaders.Add("accept", "*.*");
c.DefaultRequestHeaders.Add("referer", "https://212.112.76.21/details");
c.DefaultRequestHeaders.Add("cookie", "__cfduid=db20875432124; _gl_eu=2.66390154.1603632124; anid=^%^24223%^22; _ta=33222;");
var result = c.GetAsync($"https://123.125.212.220/details?start1=0&edl=10").Result;
}
But ultimately, I'd install Fiddler which is a tool that intercepts HTTP traffic and shows you the request and response. You can then see exactly what's going on with your Python code, and hopefully exactly what's different with your C#.