Hi. My name is*****'m a camera repair technician with over 20 years in the business and I'll be glad to help you with your question today.
Error 20 is a mechanical malfunction error code. Usually the shutter is not opening. I'm afraid this is going to require disassembling the camera to troubleshoot and repair by an experienced camera repairman. You may want to check locally for a camera repair shop in your area, or, if you need assistance finding a shop, please let me know and I'll locate one for you.
Just a note to see if I can be of any further assistance?