When someone's throwing a hissy fit, they scream and cry and they might throw things in anger. It's similar to what a child would do at a supermarket, if they didn't get the toy they wanted. You throw a hissy fit if things are not going your way. It's similar to throwing a tantrum. I don't know about the Portuguese word, sorry.
Swanning is a type of movement where you don't care about anyone or anything. A person who swans in will walk into the room with a phone in one hand and a packet of crisps in the other, leaving a trail of crumbs behind them, ignoring the fact that others are having a conversation, and probably sitting down in someone else's place.
An interesting fact is that people who swan into rooms are often ones capable of throwing hissy fits :)