How to make pictures not disappear from picturebox when minimized or saved?

Question

C++ / C#

Hello. There is a Windows Form in which - PictureBox. Everything is drawn on it, how to transfer the drawing to a Bitmap? I know you can't draw on controls, etc. Now I don't know how to change

namespace GraphicApp_v3
{
    public partial class Form1 : Form
    {
        Bitmap bitmap;
        Graphics g;
        bool isPressed = false;
        List<Point> list = new List<Point>();
        bool flag = false;
        int currentX, currentY;

        public Form1()
        {
            InitializeComponent();
            Bitmap bitmap = new Bitmap(pictureBox1.Width, pictureBox1.Height);
            g = pictureBox1.CreateGraphics();
            
        }

        private void panel3_Paint(object sender, PaintEventArgs e)
        {

        }

        public void Rectangle()
        {
            g.TextRenderingHint = System.Drawing.Text.TextRenderingHint.AntiAlias;
            Rectangle Rect = new Rectangle(currentX, currentY, 150, 75);
            g.FillRectangle(Brushes.White, Rect);
            g.DrawRectangle(new Pen(Color.Black, 2), Rect);
            StringFormat sf = new StringFormat();
            sf.Alignment = StringAlignment.Center;
            sf.LineAlignment = StringAlignment.Center;
            g.DrawString(textBox1.Text, new Font("Times", 12), Brushes.Black, Rect, sf);
        }

        public void Cucl()
        {
            Point[] points = new Point[6]
            {
                new Point(currentX, currentY),
                new Point(currentX+50, currentY+40),
                new Point(currentX+105, currentY+40),
                new Point(currentX+160, currentY),
                new Point(currentX+105, currentY-40),
                new Point(currentX+50, currentY-40)};
            g.TextRenderingHint = System.Drawing.Text.TextRenderingHint.AntiAlias;
            g.FillPolygon(Brushes.White, points);
            g.DrawPolygon(new Pen(Color.Black, 2), points);
            StringFormat sf = new StringFormat();
            sf.Alignment = StringAlignment.Center;
            sf.LineAlignment = StringAlignment.Center;
            float[] data = new float[points.Length];
            for (int i = 0; i < points.Length; i++)
            {
                data[0] = points[i].X;
                data[1] = points[i].Y;
                data[2] = points[i].X;
                data[3] = points[i].Y;
            }
            g.DrawString(textBox1.Text, new Font("Times", 12), Brushes.Black, data[0]+30, data[1]+35, sf);
        }

        public void Rectangle_Naklon()
        {
            Point[] points = new Point[4]
            {
                new Point(currentX, currentY),
                new Point(currentX-15, currentY+70),
                new Point(currentX+140, currentY+70),
                new Point(currentX+155, currentY)
            };
            g.TextRenderingHint = System.Drawing.Text.TextRenderingHint.AntiAlias;
            g.FillPolygon(Brushes.White, points);
            g.DrawPolygon(new Pen(Color.Black, 2), points);
            StringFormat sf = new StringFormat();
            sf.Alignment = StringAlignment.Center;
            sf.LineAlignment = StringAlignment.Center;
            float[] data = new float[points.Length];
            for (int i = 0; i < points.Length; i++)
            {
                data[0] = points[i].X;
                data[1] = points[i].Y;
                data[2] = points[i].X;
                data[3] = points[i].Y;
            }
            g.DrawString(textBox1.Text, new Font("Times", 12), Brushes.Black, data[0]-80, data[1]+30, sf);
        }

        public void Uslovue()
        {
            Point[] points = new Point[4] { new Point(currentX,currentY), new Point(currentX + 75,currentY+50), new Point(currentX+150,currentY), new Point(currentX+75,currentY-50)};
            g.TextRenderingHint = System.Drawing.Text.TextRenderingHint.AntiAlias;
            g.FillPolygon(Brushes.White, points);
            g.DrawPolygon(new Pen(Color.Black, 2), points);
            StringFormat sf = new StringFormat();           
            sf.Alignment = StringAlignment.Center;
            sf.LineAlignment = StringAlignment.Center;
            float[] data = new float[points.Length];
            for (int i = 0; i < points.Length; i++)
            {
                data[0] = points[i].X;
                data[1] = points[i].Y;
                data[2] = points[i].X;
                data[3] = points[i].Y;
            }
            g.DrawString(textBox1.Text, new Font("Times", 12), Brushes.Black, data[0], data[1]+50, sf);
        }

        public void Start_End()
        {
            g.TextRenderingHint = System.Drawing.Text.TextRenderingHint.AntiAlias;
            Rectangle Rect = new Rectangle(currentX, currentY, 75, 40);
            g.FillEllipse(Brushes.White, Rect);
            g.DrawEllipse(new Pen(Color.Black, 2), Rect);
            StringFormat sf = new StringFormat();
            sf.Alignment = StringAlignment.Center;
            sf.LineAlignment = StringAlignment.Center;
            g.DrawString("Начало", new Font("Times", 12), Brushes.Black, Rect, sf);
        }

        public void End()
        {
            g.TextRenderingHint = System.Drawing.Text.TextRenderingHint.AntiAlias;
            Rectangle Rect = new Rectangle(currentX, currentY, 75, 40);
            g.FillEllipse(Brushes.White, Rect);
            g.DrawEllipse(new Pen(Color.Black, 2), Rect);
            StringFormat sf = new StringFormat();
            sf.Alignment = StringAlignment.Center;
            sf.LineAlignment = StringAlignment.Center;
            g.DrawString("Конец", new Font("Times", 12), Brushes.Black, Rect, sf);
        }
        

        private void button1_Click(object sender, EventArgs e)
        {
            pictureBox1.Refresh();
        }

        private void button2_Click(object sender, EventArgs e)
        {
         
            if (saveFileDialog1.ShowDialog() == DialogResult.OK)
            {
                Bitmap bitmap = new Bitmap(pictureBox1.Width, pictureBox1.Height);
                pictureBox1.DrawToBitmap(bitmap, new Rectangle(0, 0, bitmap.Width, bitmap.Height));
                bitmap.Save(saveFileDialog1.FileName);


            }
        }
        
        

        private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
        {
            currentX = e.X;
            currentY = e.Y;
            label1.Text = currentX.ToString();
            label2.Text = currentY.ToString();
        }

        private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
        {
            isPressed = true;
            
            if (radioButton8.Checked == true)
            {
                if (flag)
                {
                    list.Add(new Point(e.X, e.Y));
                    g.DrawLines(new Pen(Color.Black, 2), list.ToArray());
                }
                else
                {
                    list.Add(new Point(e.X, e.Y));
                    flag = true;
                }
                if (list.Count >= 2)
                {
                    list.Clear();
                    flag = false;
                }

            }

            if (radioButton4.Checked == true)
            {
                if (isPressed)
                {
                    Rectangle();
                }
            }

            if (radioButton5.Checked == true)
            {
                if (isPressed)
                {
                    Uslovue();
                }
            }

            if (radioButton1.Checked == true)
            {
                if (isPressed)
                {
                    Start_End();
                }
            }

            if (radioButton2.Checked == true)
            {
                if (isPressed)
                {
                    End();
                }
            }

            if (radioButton3.Checked == true)
            {
                if (isPressed)
                {
                    Rectangle_Naklon();
                }
            }

            if (radioButton6.Checked == true)
            {
                if (isPressed)
                {
                    Cucl();
                }
            }
        }

        private void pictureBox1_MouseUp(object sender, MouseEventArgs e)
        {
            isPressed = false;
        }
    }
}

Answer 1

All drawing is well done. But the onpaint event for you, Trump will process?
In general, you create a bitmap. Next call
Graphics grfx = Graphics.FromImage(bitmap);
You draw drawings not on the control, but on the bitmap, and then on the control you draw the bitmap.
override the onpaint event and draw your bitmap in it again.