Guild Wars 2

Hey guys !
Just came back to the game after a prolonged period of abscence (I used to play before the new story arcs came out, no idea what those are actually). And I used to play a warrior and (ok not a lot mostly the warrior) a thief. Could you tell me what’s changed mainly and any tips ?
Thanks in advance !

I’ve started downloading the game and I was just wondering how big it is so I can know approximatly how long it’ll take. Thanks in advance for the answers