My Poloniex Account Has been Compromised Today

Today when I receive an email of showing a withdrawl request in subject line from poloniex, I was shocked because it was not me. After that I view that a code email received in my inbox, I again shocked whats going on and finally received an email successful login, everything was really shocked for me. I click on the link where it was written "Freeze your account" if you are not login, I click on it from my mobile and find that link was brocken and it shows "oops sorry there is no page available".

My laptop was not near me. The only way to come out from the situation was my 4g enabled android mobile, then I click on poloniex support center and generate a ticket in which I mentioned that my account is hacked and please freeze it immediately. Meanwhile I reach to home and start my laptop and then check the details, there was 2 time successful login, which was not a mistake, the IP was of any other country(hackers country, or hackers IP).

Then in withdrawl email, I copy the link of transaction and check it in blockchain transaction checker and then I feel good that no withdrawl/deposits done in this transaction. Now I'm not able to access my account right now, poloniex agent is working to chek my account activity details, I don't know what type of activities Mr. Hacker has done in my account but I'm quite sure that he was very near to withdraw amount from my poloniex account and I change passwords of my poloniex account and gmail id, now after accessing my account, I will impose 2F protection but its really dangrous experience. anybody have any experience like this, anybody lost amount through this type of activity because these platforms like poloniex hide these type of stories from clients, they have closed the "Troll box" because people share their loses in troll box.
Expected activities of hacker were:

He sale my altcoins and balance was available in Bitcoin, because my poloniex coins were in small coins and hacker withdrawl request shows only "BTC" of almost total amount. Then he tried to withdraw that btc from my account and he was 80% done but finally what happened(all black box). Can anybody explain what is procedure of hackers.