Guys my Cryptopia Account got hacked and all my coins got sold and stolen... by a user called kagevu... what can i do?

How could that happen, the password in cryptopia was not just numbers and letters only. but must also use some characters.
How can it be hacked, do you not use two factor security ?
Theirs someone also trying to broke in unto my account but sad to say he did not succeed on his bad attempts since my 2FA is activated and it make me safe for this for a while and I don't know why hacker track my account while im so carefull upon dealing with gmails on some sites when I register and I'm not using the email of my exchange upon signing on bounties or other altcoin and giveaways scene.
So 2FA activation is very advisable so that this hacking issue will not occur again.