Best practices to handle Web API status codes - rest

Question

I have a web API project done with .NETCore.
My web API receives a request from another Service A, with the information I have I need to do some conversion on the data and send it to another Service B.
I am expecting that Service B send back some response: like OK or NOK. As the number of codes I can get back from Service B are so much. I would like to know which is the best practices to handle those codes?
As you will see in my code, I get the status code in this way:
var status = (int)response.StatusCode;
And the I have some if to handle this. Looking at my code it looks like a very poor status code Handling but at moment it is the best I can do. I am kindly asking suggestions to improve this.
I am using RestSharp.
Following my code:
[HttpPost]
[Produces("application/json", Type = typeof(MyModel))]
public async Task<IActionResult> Post([FromBody]MyModel myModel)
{
try
{
if (!ModelState.IsValid)
{
return BadRequest(ModelState);
}
var response = (RestResponse) await _restHelper.GetResponse("ServiceB:url", myModel);
if (response != null)
{
var status = (int)response.StatusCode;
//2xx status OK
if (status >= 200 && status < 300)
{
return Ok(response.Content);
}
//Catch all status code
return StatusCode(status, response.Content);
}
//If for some reason, I don't get any response from ServiceB
return NotFound("No response from ServiceB");
}
catch (Exception ex)
{
_logger.LogError("POST_ERROR", "ServiceB-relay/Post UNEXPECTED ERROR", ex.Message);
return StatusCode(500, "Server error, not able to process your request");
}
}
and this is my restHelper
public class RestHelper: IRestHelper
{
private readonly IConfigurationRoot _config;
public RestHelper(IConfigurationRoot config)
{
_config = config;
}
public async Task<IRestResponse> GetResponse(string configKey, object dtoObject)
{
//Get the URL from the config.json
var url = _config[configKey];
//Create rest client and rest request
var restClient = new RestClient(url);
var request = new RestRequest {Timeout = 30000, Method = Method.POST};
//Add header
request.AddHeader("Accept", "application/json");
//convert the dto object to json
var jsonObject = JsonConvert.SerializeObject(dtoObject.ToString(), Formatting.Indented);
request.AddParameter("application/json", jsonObject, ParameterType.RequestBody);
var taskCompletion = new TaskCompletionSource<IRestResponse>();
//Execute async
restClient.ExecuteAsync(request, r => taskCompletion.SetResult(r));
//await the task to finish
var response = (RestResponse) await taskCompletion.Task;
return response;
}
Thanks