Hello tmtegypt,

I'm sorry to hear you are having these issues with your iMac. I also apologize, I'm a bit unclear on the exact nature of your question or current configuration. If you are having issues with the exeternal display connected to your iMac, you may find the information and troubleshooting steps outlined in the following articles helpful:

OS X Yosemite: Connect multiple displays to your Mac

Apple computers: Troubleshooting issues with video on internal or external displays - Apple Support

Sincerely,

- Brenden