https://twitter.com/nzpolice/status/1098367362347163648
https://twitter.com/Cryptopia_NZ/status/1096158617022201856i check my btc adress today, but on 2019-02-08 01:32:56 they are send to another btc adress. my balance is now: 0 BTC

This is normal for a deposit to an exchange: the funds are often swept into another wallet, or used for fulfilling another customer's withdraw.
Just like if you deposit a $10 note at the bank, your balance remains $10, even though that same physical bank note may end up in another customer's hands.
I can't state categorically that your funds are safe at Cryptopia, just that you should not be alarmed by your deposit address showing a balance
(on the blockchain) of zero.
That is correct. When you send a deposit to an exchange it is sent to an individual deposit address. It is then swept to a hot-wallet or cold storage.
The value of the deposit is transferred via the deposit engine to the exchange ledger. After a set number of confirmations it is then made available on the exchange ledger for trading. The actual amount deposited it kept in a general wallet with other deposits.
Until you withdraw the amounts that you see in on your account are only on the exchange ledger - not on the blockchain.
While it is possible to send deposits to your exchange deposit address and to a hot wallet or cold-wallet address. It will show on the blockchain but unless Cryptopia deposit engine is working will not show on your account balance.
DO NOT SEND ANY DEPOSITS TO CRYPTOPIA until they say it is safe to do so. It is unclear whether any of the deposit addresses are safe to deposit to.
If they have lost access to the private key of a blockchain address then you are effectively sending it to the hacker directly.