Greetings, Kaliktus! My name is Arif, and I will assist you today.
I am sorry to hear that you are facing this issue. The only option to regain access to your computer is by entering the Bitlocker key. If you haven't backed up the Bitlocker key before, you need to log in to your Microsoft account on another device and check if you are able to find your Bitlocker key. Especially if you remember the account that was logged into your computer, on the Bitlocker page, you will find an ID. Match this ID with each of your Microsoft accounts. If the ID matches, you can enter that Bitlocker key to unlock your computer.
Link: https://account.microsoft.com/devices/recoveryk...
Finding your BitLocker recovery key in Windows:
https://support.microsoft.com/en-us/windows/fin...
Warm Regards,
Arif