The current fastest and cheapest transaction fee is 420 satoshis/byte according to bitcoinfees.21.co (while you only paid 155 satoshis/byte) so Its probably a fee issue, your transaction will take sometime but eventually get confirmed and you will see it in your account as completed so no, there is nothing to be worried about.

As for the second problem, Poloniex should give you the TXID so you should show it to the Livecoin support. Livecoin is somehow a new exchange so I'm going to assume that the problem is either coming from them or you sent the funds to the wrong address.