First time playing with moving graphics and intersects

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Timers;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace UselessV1
{
    public partial class Form1 : Form
    {
        System.Timers.Timer timer;
        Rectangle character;
        Rectangle block;

        SizeF charSize;
        Boolean left, right, up, down, gameover;

        int hp, gameoverSize;
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            this.KeyDown += Form1_KeyDown;
            this.KeyUp += Form1_KeyUp;


            //Create the first position and size
            character.X = 10;
            character.Y = 10;
            charSize = new SizeF(10, 10);

            character.Height = (int)charSize.Height;
            character.Width = (int)charSize.Width;

            hp = 100;
            gameoverSize = 0;
            //block

            block.X = 100;
            block.Y = 100;
            block.Height = 20;
            block.Width = 20;

            //Add timer
            timer = new System.Timers.Timer(33);
            timer.Elapsed += update;
            timer.Start();
        }

        private void Form1_KeyDown(object source, KeyEventArgs e){
            switch (e.KeyCode)
            {
                case Keys.Left:
                    left = true;
                    right = false;
                    break;
                case Keys.Right:
                    right = true;
                    left = false;
                    break;
                case Keys.Up:
                    up = true;
                    down = false;
                    break;
                case Keys.Down:
                    down = true;
                    up = false;
                    break;
            }
        }

        private void Form1_KeyUp(object source, KeyEventArgs e)
        {
            switch (e.KeyCode)
            {
                case Keys.Left:
                    left = false;
                    break;
                case Keys.Right:
                    right = false;
                    break;
                case Keys.Up:
                    up = false;
                    break;
                case Keys.Down:
                    down = false;
                    break;
            }
        }

        private void update(object source, EventArgs e)
        {
            if (gameover != true)
            {
                if (up)
                {
                    character.Y -= 10;
                }

                if (down)
                {
                    character.Y += 10;
                }

                if (left)
                {
                    character.X -= 10;
                }

                if (right)
                {
                    character.X += 10;
                }

                if (character.IntersectsWith(block))
                {
                    hp -= 5;
                }

                if (hp <= 0)
                {
                    gameover = true;
                }

                this.draw();
            }
            else
            {
                gameoverSize++;
                this.endGame();

                if (gameoverSize >= 25) {
                    timer.Stop();
                }
            }
        }

        private void draw()
        {

            Graphics g = this.CreateGraphics();

            g.Clear(Color.FromName("Control"));

            Font font = new Font(FontFamily.GenericSansSerif, 12);


            Brush blackBrush = new SolidBrush(Color.Black);
            Pen blackPen = new Pen(blackBrush);

            Brush redBrush = new SolidBrush(Color.Red);
            Pen redPen = new Pen(redBrush);

            g.DrawString("Health: " + hp + "%", font, blackBrush, new PointF(5, 5));
            g.DrawRectangle(blackPen, character);
            g.DrawRectangle(redPen, block);

            g.Dispose();
        }

        private void endGame()
        {


            Graphics g = this.CreateGraphics();

            g.Clear(Color.FromName("Control"));

            Font font = new Font(FontFamily.GenericSansSerif, gameoverSize);


            Brush blackBrush = new SolidBrush(Color.Black);
            Pen blackPen = new Pen(blackBrush);
            string text = "Game Over";

            g.DrawString(text, font, blackBrush, new PointF((this.Width / 2) - (this.Width / 4), ((this.Height / 2) - font.Height) - 5));

            g.Dispose();
        }
    }
}