Could someone explain to me why the transaction from Bittrex can't be seen on Etherscan Xaurum Token Tracker? Example: There was a transaction on Bittrex at 11:12:50 when somebody bought 40985.37 Xaurums. That transaction can't be find on Etherscan Xaurum Token Tracker. Why is that so?
When one buys or sells on an exchange, no (blockchain) transaction is actually performed, these are just numbers ... As nmrcngrb pointed out, withdraw and deposit operations are the one who generate transactions that are visible on explorers.
so there's also no transaction fees? and no burning (0.5 xaur atm) when transaction happens on the exchanges?
The exchange takes its fees on any financial (buy or sell) transaction. It also takes fees when you withdraw, that is a blockchain transaction which implies a standard fee. For Xaurum there's the gas (ETH) + the burning fee, the exchange surely takes this into account when setting a withdraw fee.
When you buy or sell Xaurum (or any asset on an exchange), the only fees are the ones taken by the exchange (taker/maker type of fees), the bockchain is not affected by these operations so there is no blockchain transaction (and in case of Xaurum no burning fee). The transaction fee (+ the burning fee) only concerns blockchain transfers, in case of an exchange, these are deposits and withdrawals.