If you fear about your data, change your password and don't use the same in more than 1 of your accounts. Of course don't use exchanges or any other wallet type that don't allow you to have your private keys.
This is good advice to secure your coins. This does nothing to secure your data. It doesn't matter how secure your account is, how strong your password is, what 2FA you have activated; if the exchange's database gets hacked or they decide to sell information to third parties, then say goodbye to your data and your privacy.
but I don't know how the hackers managed to bypass the 2Factor Authentication.I guess that there was a flaw in the 2FA system,which was exploited.
As I explained above, SMS as a 2FA method is not in the least bit secure. Neither is an email for that matter, since if an attacker can access your email account to reset your password, they can also receive any 2FA code, meaning your account is only secured by one factor - your email account. Both of these methods are barely better than not using any 2FA at all. If you want secure 2FA you should be using a 2FA app on a device which never logs in to any of your accounts as a minimum, put preferably a hardware key.