if I've created account/wallet on coinbase or any other exchange then my account is hacked and my coins/money lost who are responsible for it
The Exchange where I've created account
is it my mistake
what's you thought about it
and how i make my account safe
If the exchange is compromised then it's exchange's fault and the responsibility is totally upon the exchange.
Yes if only your accounts are hacked it can be your fault that you may have used a weak password or have low security.
I believe in both cases responsibility is up to you because no one force you to keep your bitcoins on any exchange right? Why do you want to trust any third party with your coins? Store in offline or at least somewhere safe?
If an exchange is hacked or something's happen still it is your fault, not anyone.
I would like to say that you should keep your coins safe not on an exchange or any other place or at least use layers-of-security such as 2fa, email, etc.