JSon PHP Converter for C #

Hello, I'm having trouble converting a PHP API to be used in C #, I can connect to the API but I can not send data, could anyone help me?

Follow the PHP API:

$process = curl_init("URL API");
    curl_setopt($process, CURLOPT_USERPWD, "USUARIO:SENHA");
    curl_setopt($process, CURLOPT_TIMEOUT, 30);
    curl_setopt($process, CURLOPT_RETURNTRANSFER, TRUE);
    curl_setopt($process, CURLOPT_POST, true);
    curl_setopt($process, CURLOPT_POSTFIELDS, array(
        "establishment" => $establishment,
        "username" => $usuario,
        "password" => $senha,
        "name" => $nome,
        "email" => $email,
        "cpf" => $cpf,
        "login_expiration" => $expirarLogin,
        "profile_id" => $perfil
    ));

    if(json_decode(curl_exec($process)) === false){
        return FALSE;
    }else{
        return TRUE;
    }

Here's what I've been able to do so far using C #:

using RestSharp;

var cookie = new CookieContainer();
var client = new RestClient("URL API") {
  Authenticator = new HttpBasicAuthenticator("USUARIO", "SENHA"),
    CookieContainer = cookie
};

var request = new RestRequest(Method.POST);
//var process = new RestClient(Method.POST);
//request.AddParameter(""", "projectID=729-11230-1", ParameterType.RequestBody);
//request.AddParameter("application/x-www-form-urlencoded", "name=Example backlog item 1", ParameterType.RequestBody);

//request.AddParameter("application/x-www-form-urlencoded", "establishment=sesc_new", ParameterType.GetOrPost);
//request.AddParameter("application/x-www-form-urlencoded", "username=user", ParameterType.GetOrPost);
//request.AddParameter("application/x-www-form-urlencoded", "password=senha", ParameterType.GetOrPost);
//request.AddParameter("application/x-www-form-urlencoded", "name=Teste API Sharp", ParameterType.GetOrPost);
//request.AddParameter("application/x-www-form-urlencoded", "email=email", ParameterType.GetOrPost);
//request.AddParameter("application/x-www-form-urlencoded", "cpf=cpf", ParameterType.GetOrPost);
//request.AddParameter("application/x-www-form-urlencoded", "login_expiration=2018-07-20 23:59:59", ParameterType.GetOrPost);
//request.AddParameter("application/x-www-form-urlencoded", "profile_id=4080", ParameterType.GetOrPost);

IRestResponse response = client.Execute(request);

MessageBox.Show(response.Content);

I can make the connection, but now I do not know how to send the information to the API from C #.