private void Form1_Load(object sender, EventArgs e)
    {
        progressBar2.Minimum = 1;
        progressBar2.Maximum = nummax;
    }

private void timer2_Tick(object sender, EventArgs e)
{
    for (int i = 1; i <= nummax; i++)
    {
        if (i != nummax && !enabled)
        {
            int percent;
            percent = i / nummax;
            string ab = percent.ToString();
            progress.Text = ab;
            Thread.Sleep(50);
            progressBar2.Value = i;
        }
    }
    if (progressBar2.Value == nummax || enabled || progressBar2.Value >= nummax - 30)
    {
        progress.Text = "Completed!";
        progressBar2.Minimum = 1;
        progressBar2.Maximum = 2;
        enabled = true;
    }
}

private async void timer2_Tick(object sender, EventArgs e) {
     ...
     // Thread.Sleep(50); blocks when Task.Delay(50); doesn't
     await Task.Delay(50);
     ...
   }