How to stop Decryption process.

I am trying to update my OS, it is not working getting errors saying check conversations or decryption process is not finished. My MacBook has been decrypting for 7 days, 7 DAYS. I have tried, repairing, verifying, command R and back up. Nothing. I tried terminal and deleting long numbers. Nothing works. My computer is moving super super super slow. The laptop is empty, no files , so if someone can walk me through the reforming. I even tried reformatting the hard drive, but it say that the computer needs to finish the decrypting process, oh yea, it's been 7 days. Help