Create a Web Api that calls another Web Api

I created an Api Web here in my work to be consumed by my Xamarin Forms project. 100% running smoothly ... Then I was informed that in fact here is used 2 web api's for security. That is, I will have to create a web-based Api ("frontend") with external access, which would function as a doorman, passing the calls to another Web Api ("backend") and this one only has access to DB and only accepts internally . As I'm a beginner and I took a beating to get this Web Api to work and it works, I'd like some help on how to do this. I would have to call the WebApi 1 and it will carry the values entered by the user up to the Web Api 2 ... this in turn will have the database calls and all the controllers ... after the query is that I did not understand the what to do, because the data is spit on Json and a good part I was able to make it work in the search.

My code in Xamarin:

ApiCall apiCall = new ApiCall();

                apiCall.GetResponse<List<Envolvido>>("nomes", "Envolvidos", nomepesquisa, nomemae, nomepai, dtnasc, nrg, ncpf).ContinueWith(t =>
               {
                   //Aqui verificamos se houve problema ne requisição
                   if (t.IsFaulted)
                   {
                       Debug.WriteLine(t.Exception.Message);
                       Device.BeginInvokeOnMainThread(() =>
                       {
                           DisplayAlert("Falha", "Ocorreu um erro na Requisição :(", "Ok");
                           //IsBusy = false;
                       });
                   }
                   //Aqui verificamos se a requisição foi cancelada por algum Motivo
                   else if (t.IsCanceled)
                   {
                       Debug.WriteLine("Requisição cancelada");

                       Device.BeginInvokeOnMainThread(() =>
                       {
                           DisplayAlert("Cancela", "Requisição Cancelada :O", "Ok");
                           //IsBusy = false;

                       });
                   }

                   //Caso a requisição ocorra sem problemas, cairemos aqui
                   else
                   {
                       //Se Chegarmos aqui, está tudo ok, agora itemos tratar nossa Lista
                       //Aqui Usaremos a Thread Principal, ou seja, a que possui as references da UI
                       Device.BeginInvokeOnMainThread(() =>
                          {
                              //IsBusy = false;
                              ListaDados.ItemsSource = t.Result;
                              var count = ListaDados.ItemsSource.OfType<object>().Count();
                              if (count == 0)
                              {
                                  DisplayAlert("Cancela", "Não há dados retornados.", "Ok");
                              }
                              else
                                  Navigation.PushAsync(new ResultadosBuscados(ListaDados.ItemsSource));
                          });

                   }

part of my ApiCall that calls the Api Web:

public class ApiCall
    {
        static readonly string ApiUrl = "http://Localhost:1762/api/{0}/{1}?nomePesquisa={2}&nomeMae={3}&nomePai={4}&dtNasc={5}&nrg={6}&ncpf={7}";

            public async Task<T> GetResponse<T>(string controller, string method, string nomepesquisa, 
            string nomemae, string nomepai, string dtnasc, string nrg, string ncpf) where T : class
        {
            var client = new System.Net.Http.HttpClient();


            client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));


            var urllink = string.Format(ApiUrl, controller, method, nomepesquisa, nomemae, nomepai, dtnasc, nrg, ncpf);
            var response = await client.GetAsync(urllink);

            //Lê a string retornada
            var JsonResult = response.Content.ReadAsStringAsync().Result;

            if (typeof(T) == typeof(string))
                return null;

            //Converte o resultado Json para uma Classe utilizando as Libs do Newtonsoft.Json
            var rootobject = JsonConvert.DeserializeObject<T>(JsonResult);
            return rootobject;
        }
}

My controller code in Api Web:

[RoutePrefix("api/nomes")]
    public class NomesController : ApiController
    {
        public string GetConnectionString()
        {
            string MeuConnString = "Data Source=(DESCRIPTION ="
                + "(ADDRESS=(PROTOCOL = TCP)(HOST = xxx)(PORT = xxx))"
                + "(CONNECT_DATA = (SERVER = DEDICATED)(service_name = xxx)));"
                + "User Id = xxx; Password=xxx";
            return MeuConnString;
        }


        [HttpGet]
        [Route("Envolvidos")]
        public IEnumerable<Envolvido> GetEnvolv(string nomePesquisa, string nomeMae, string nomePai, string dtnasc
            , string nRG, string nCPF)
        {

            DataSet lretorno = new DataSet();

            string connectionString = GetConnectionString();
            using (OracleConnection connection = new OracleConnection())
            {
                connection.ConnectionString = connectionString;

                OracleDataReader reader = null;
                OracleCommand cmd = new OracleCommand();
                cmd.Connection = connection;
                cmd = new OracleCommand("MOBILE.XAPIMAND.BUSCAPOSCANDIDOSPF", connection);
                cmd.CommandType = CommandType.StoredProcedure;

                //variáveis entrada            
                cmd.Parameters.Add(new OracleParameter("ivnome",nomePesquisa));
                cmd.Parameters.Add(new OracleParameter("ivmae", nomeMae));
                cmd.Parameters.Add(new OracleParameter("ivpai", nomePai));
                cmd.Parameters.Add(new OracleParameter("ivdatanasc", dtnasc));
                cmd.Parameters.Add(new OracleParameter("ivrg", nRG));
                cmd.Parameters.Add(new OracleParameter("icpf", nCPF));
                //variáveis de saida          
                cmd.Parameters.Add(new OracleParameter("oretorno", OracleDbType.RefCursor)).Direction = ParameterDirection.Output;
                cmd.Parameters.Add(new OracleParameter("qretorno", OracleDbType.RefCursor)).Direction = ParameterDirection.Output;

                connection.Open();
                cmd.ExecuteNonQuery();

                reader = cmd.ExecuteReader(CommandBehavior.CloseConnection);

                //CRIO A LISTA
                lretorno.Load(reader, LoadOption.OverwriteChanges, "BUSCAPOSSIVEISCANDIDATOSPF");
                connection.Close();
                connection.Dispose();


                //CARREGO O DATASET E TRANSFORMO PARA IENUMERABLE E RETORNO SEUS VALORES PRO JSON
                return lretorno.Tables[0].AsEnumerable().Select(row => new Envolvido
                {
                    SUSPID = Convert.ToInt32(row["SUSPID"]),
                    IVNOME = Convert.ToString(row["SUSPNOME"]),
                    IVMAE = Convert.ToString(row["SUSPMAE"]),
                    IVPAI = Convert.ToString(row["SUSPPAI"]),
                    IVDATANASC = Convert.ToString(row["SUSPDATANASC"]).Replace(" 00:00:00", ""),
                    IVRG = Convert.ToString(row["RG"]),
                    ICPF = Convert.ToString(row["CPF"]),
                    MANDADO = Convert.ToInt16(row["TEMMANDADO"]),
                    OCORRENCIA = Convert.ToInt16(row["TEMOCORRENCIA"]),

                });


            }
        }

    }