Is possible to auto lock drive with bitlocker when the laptop go on standby or sleep mode?
Or when the user is changed?
I want the drive to be accesible only by one user.
This is not what Bitlocker is for.
Full Disk Encryption (FDE) tools like Bitlocker are only meant to protect against off-line attacks. This is where the computer's operating system is not running.
Examples might be if the disk is removed and mounted in another computer, or if the computer is booted from a LiveCD or similar.
When the OS is running - which includes when the laptop is in standby - then it is the OS's job to protect the contents of the disk.