How to send a photo to telegram?

Question

C++ / C#

I always get this as a response:

{"ok":false,"error_code":400,"description":"Bad Request: there is no photo in the request"}

THE CODE:

#include <windows.h>
#include <wininet.h>
#include <iostream>
#include <fstream>
#include <string>
#include <sstream>

using namespace std;

#pragma comment(lib, "wininet")

string postRequest(string url, string path, string postData) {
  HINTERNET hInternet, hConnect, hRequest;
  hInternet = InternetOpen(TEXT("TERNICK OWL"), INTERNET_OPEN_TYPE_PRECONFIG, NULL, NULL, 0);
  if (hInternet != NULL) {
    hConnect = InternetConnect(hInternet, TEXT(url.c_str()), INTERNET_DEFAULT_HTTP_PORT, NULL, NULL, INTERNET_SERVICE_HTTP, 0, 1u);
    if (hConnect != NULL) {
      hRequest = HttpOpenRequest(hConnect, TEXT("POST"), path.c_str(), NULL, NULL, NULL, INTERNET_FLAG_KEEP_CONNECTION | INTERNET_FLAG_RELOAD, 1);
      if (hRequest != NULL) {
        string headers = "Content-Type: multipart/form-data; boundary=bf113e6d618f47f7b56337cafdf3c036";
        BOOL bSend = HttpSendRequest(hRequest, headers.c_str(), headers.size(), (LPVOID)postData.data(), (DWORD)postData.size());
        if (bSend) {
          DWORD dwSize = 0;
          string result;
          char *buff = new char[256];
          do
          {
            memset(buff, 0, 256);
            InternetReadFile(hRequest, buff, sizeof(buff) - 1, &dwSize);
            result.append(buff, dwSize);
          } while (dwSize != 0);
          delete[] buff;
          InternetCloseHandle(hRequest);
          InternetCloseHandle(hConnect);
          InternetCloseHandle(hInternet);
          return result;
        }
        else {
          InternetCloseHandle(hRequest);
          InternetCloseHandle(hConnect);
          InternetCloseHandle(hInternet);
        }
      }
      else {
        InternetCloseHandle(hRequest);
        InternetCloseHandle(hConnect);
        InternetCloseHandle(hInternet);
      }
    }
    else {
      InternetCloseHandle(hConnect);
      InternetCloseHandle(hInternet);
    }
  }
  else {
    InternetCloseHandle(hInternet);
  }
  return "";
}

string slurp(string path) {
  stringstream sstr;
  ifstream in(path, ios::out | ios::binary);
  sstr << in.rdbuf();
  in.close();
  return sstr.str();
}
int main() {
  string response = postRequest("api.telegram.org", "bot<TUTTOKEN>/sendPhoto?chat_id=429037951&caption=CAP", "--bf113e6d618f47f7b56337cafdf3c036\nContent-Disposition: form-data; name=\"photo\"; filename=\"photo\"\n\n" + slurp("screen.bmp")) + "--bf113e6d618f47f7b56337cafdf3c036--";
  cout << response << endl;
  system("pause");
  return 0;
}

AAA HELP :)
Tried to imitate python requests but didn't work.