Issue with export audio mixdown screen

I wonder if anyone out there could help me. I am self taught at using Cubase 8 pro. I have used Cubase now for many years. When i go to file then export, audio mix, and the screen pops up. The window fills my whole screen, I then try to drag the window upwards so as to click on the export button below and the screen will not move. So therefore i am unable to export my mix. Does anyone know how to solve this problem or is there a shortcut key to command it to export? I’d be very greatful for any help that anyone could give me. Many thanks! Natasha from United Kingdom