encryption – Can I recover my data again? HELP

About 2 weeks ago I was doing a decryption to a partition on an external hard drive. – Encryption type: (Bitlocker encryption). But, unfortunately, my laptop had shut down during the operation. Since then, I have tried to open it in all the ways I know for 14 laborious days. I contacted Microsoft Customer Service, which did not help me at all! And he sent me a provocative replay that I should have backed him up! Even though the Bitlocker is a Microsoft service!
Is it possible to return it? And how this information is my job for 20 years.