test

private void button1_Click(object sender, EventArgs e)
        {
            timer1.Start();
            Label[] label = new Label[] { label2,label3, label4, label5, label6, label7, label8, label9, label10, label11, label12,label13 };
            for (int i = 0; i < 12; i++)
                slova[i] = label[i].Text;

            if (!button1.Enabled)
                return;
            if (button1.Text == "Start")
            {
                i = 0;
                timer1.Enabled = true;
                button1.Text = "Stop";
                button1.Enabled = true;
            }
            else
            {
                label[i].Text = slova[i];
                i = i + 1;
                if (i == 12)
                {
                    textBox1.Enabled = true;
                    button1.Enabled = false;
                    button1.Text = "Start";
                    timer1.Enabled = false;
                    //Vreme.Enabled = true;
                    textBox1.Focus();
                }
            }
        }

        private void timer1_Tick(object sender, EventArgs e)
        {
            char[] letters = new char[30] { 'A', 'Б', 'В', 'Г', 'Д', 'Ђ', 'Е', 'Ж', 'З', 'И', 'Ј', 'К', 'Л', 'Љ', 'М', 'Н', 'Њ', 'О', 'П', 'Р', 'С', 'Т', 'Ћ', 'У', 'Ф', 'Х', 'Ц', 'Ч', 'Џ', 'Ш' };
            Label[] label = new Label[] { label2,label3, label4, label5, label6, label7, label8, label9, label10, label11, label12, label13 };

            string randomString = "";
            for (int i = 0; i < 12; i++)
            {
                randomString += letters[rand.Next(0, 30)].ToString();
                label[i].Text = randomString;
            }
        }