DX issues

using DxLibDLL;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using static DxLibDLL.DX;

namespace ConsoleApplication3
{
    class Program
    {
        public static bool CloseFlag = false;
        private static int mStartTime = 0;
        private static int mCount = 0;
        private static float mFps = 0;
        private static int N = 60;
        public static int FPS = 60;
        public static bool DrawFPS = true;
        private static int sleepCount = 0;
        private static long lastUpdateTick = 0;

        private static int screen1;
        private static int screen2;
        static void Main(string[] args)
        {
            DX.SetUseDirect3DVersion(DX.DX_DIRECT3D_9EX);
            DX.SetUseVramFlag(DX.TRUE);
            DX.ChangeWindowMode(DX.TRUE);
            DX.SetMultiThreadFlag(DX.TRUE);
            DX.SetDrawScreen(DX.DX_SCREEN_BACK);
            DX.SetChangeScreenModeGraphicsSystemResetFlag(DX.TRUE);
            DX.DxLib_Init();
            DX.MakeKeyInput(0, 0, 0, 0);
            screen1 = DX.MakeScreen(640, 480);
            screen2 = DX.MakeScreen(640, 480);
            sleepCount = 0;
            while (!CloseFlag && DX.ProcessMessage() == 0 && DX.CheckHitKey(DX.KEY_INPUT_ESCAPE) == 0)
            {
                Tick();
                Thread.Sleep(1);
            }
            CloseFlag = true;
            DX.DxLib_End();
        }
        static void Tick()
        {
            if (lastUpdateTick == 0) lastUpdateTick = DX.GetNowCount();
            if (DX.ClearDrawScreen() == 0 && sleepCount <= 0)
            {
                if (mStartTime == 0)
                    mStartTime = DX.GetNowCount();
                if (mCount == N)
                {
                    int t = DX.GetNowCount();
                    mFps = 1000f / ((t - mStartTime) / (float)N);
                    mCount = 0;
                    mStartTime = t;
                }
                mCount++;
                Update(DX.GetNowCount() - lastUpdateTick);
                lastUpdateTick = DX.GetNowCount();
                Draw();
                int tookTime = DX.GetNowCount() - mStartTime;
                int waitTime = mCount * 1000 / FPS - tookTime;
                if (waitTime > 0)
                {
                    sleepCount = 0;
                }
            }
            if (sleepCount > 0) sleepCount--;
        }
        static void Draw()
        {
            DX.SetDrawScreen(screen1);
            DX.FillGraph(screen1, 0, 0, 0, 0);
            DX.DrawCircleAA(200, 200, 60, 100, DX.GetColor(128, 100, 0), DX.TRUE);
            DX.SetDrawScreen(screen2);
            DX.FillGraph(screen2, 0, 0, 0, 0);
            DX.SetDrawScreen(DX.DX_SCREEN_BACK);
            DX.DrawGraph(0, 0, screen1, DX.TRUE);
            DX.DrawGraph(0, 0, screen2, DX.TRUE);
            DX.ScreenFlip();

        }
        static void Update(long tick)
        {
        }
    }
}