I’m new to Appium and testing aswell, just set everything up today and tried my best.
After fixing many errors i get this error and i dont get smarter after reading everything about that in the internet.
This is my Appium Log :
error: Unexpected error: Error: Can’t set headers after they are sent.
at ServerResponse.OutgoingMessage.setHeader (http.js:691:11)
at ServerResponse.res.set.res.header (C:\Appiumnew\Appium\node_modules\appium\node_modules\express\lib\response.js:561:10)
at C:\Appiumnew\Appium\node_modules\appium\lib\server\controller.js:171:11
at safely (C:\Appiumnew\Appium\node_modules\appium\lib\server\helpers.js:306:5)
at next (C:\Appiumnew\Appium\node_modules\appium\lib\server\controller.js:170:5)
at C:\Appiumnew\Appium\node_modules\appium\lib\server\controller.js:187:9
at null. (C:\Appiumnew\Appium\node_modules\appium\lib\appium.js:305:7)
at null. (C:\Appiumnew\Appium\node_modules\appium\lib\devices\android\android.js:135:12)
at C:\Appiumnew\Appium\node_modules\appium\node_modules\async\lib\async.js:254:17
at C:\Appiumnew\Appium\node_modules\appium\node_modules\async\lib\async.js:157:25 context: [POST /wd/hub/session {“desiredCapabilities”:{“appPackage”:“com.strato.hidrive”,“platformName”:“Android”,“takesScreenshot”:true,“version”:“4.4.2”,“deviceName”:“Test_QS”,“app”:"C:\Users\adm\Downloads\HiDrive-debug_qs.ap]
If you need full log to help me, just ask:)
This is my C# Code:(First Test just want to make sure Appium is working correctly) 
using OpenQA.Selenium.Remote;
using System;
using Microsoft.Owin.Testing;
using OpenQA.Selenium.Appium;
using Microsoft.VisualStudio.TestTools.UnitTesting;
using System.IO;
using System.Diagnostics;
namespace Test_Appium
{
[TestClass]
public class UnitTest1
{
DesiredCapabilities capabilities = new DesiredCapabilities();
AppiumDriver driver;
[TestInitialize]
public void beforeStart()
{
capabilities.SetCapability("appActivity", "com.strato.hidrive.activity.StartActivity");
capabilities.SetCapability("appPackage", "com.strato.hidrive");
capabilities.SetCapability("browserName", "");
capabilities.SetCapability("platformName", "Android");
capabilities.SetCapability("takesScreenshot", true);
capabilities.SetCapability(CapabilityType.Version, "4.4.2");
capabilities.SetCapability("deviceName", "Test_Qs");
capabilities.SetCapability("app", @"C:\Users\adm\Downloads\HiDrive-debug_qs.apk");
driver = new AppiumDriver(new Uri("http://localhost:4723/wd/hub/"), capabilities);
}
[TestMethod]
public void TestMethod1()
{
driver.FindElementByName("Login").Click();
driver.LockDevice(10);
}
[TestCleanup]
public void AfterTest()
{
driver.Quit();
}
}
any help would be nice 
Thanks in advance…