FileVault Encryption

When FileVault is turned on, your Mac always requires that you log in with your account password.

When FileVault setup is complete and you restart your Mac, you will use your account password to unlock your disk and allow your Mac to finish starting up. FileVault requires that you log in every time your Mac starts up, and no account is permitted to log in automatically.

https://support.apple.com/en-us/HT204837

So its the same password, or will i make a new one for decryption?

By default, it's set to the same password as the account authorized to use it.  You could also use the recovery key as the filevault2 password, if you can remember it, then use your account password later, if your goal is just to decrypt the filevault disk without logging in right away.

There are times when  the Filevault password can get out of sync with the user account password, but that's not normal.  There are ways to force them to be different, but it's a hack.  When you normally reset the password, you'll normally be setting both of them to the same thing again.

Unfortunately, Filevault has its own login screen that's only set to List of Users, even if you set the login screen to Name and Password.  If you set the 2 passwords to be different, you can decrypt the Filevault disk first, then you'll get to a Name and Password screen.  If you create a standard account and set the filevault password to be different than the account password, you can then hide the Admin account.  If you change folder permissions to the standard account, you can even prevent the standard account from ever actually being able to log in.