If you cannot see no Turn off BitLocker option then this issue is caused by Windows account permissions limitation, login to the administrator account to disable BitLocker.
Right-click Windows Start button > Computer Management >Double click Local Users and Groups > Double click Users >Double click Administrator > Disable Account is disabled > click OK >Click Windows Start button > Click avatar (the circle image for the account currently signed in) >Select Administrator Account to login > Press Windows Start button >Type bitlocker > Click Manage BitLocker to enter the BitLocker Drive Encryption menu >Select Turn off BitLocker to proceed with decryption >Switch back to the user account