I am running current Bitdefender Total Security. Thanks for your help with this.
More information on rescue mode in the stated link : https://www.bitdefender.com/consumer/support/answer/29132/
(Bitdefender beta tester 2019/ 2020)
When you see the Install Windows page, tap or click Repair your computer to start the Windows Recovery Environment. In the Windows Recovery Environment, on the Choose an option screen, tap or click Troubleshoot. Tap or click iMessageapp , advanced options and then click on Startup repair. After this complete the repair and see if you are able to boot in to your computer.