Guild Wars 2

So I hit level 80 and I’m just kind of lost on what to do with the endgame. I ran the the whole game pretty much solo, and now I just feel lost. Just wondering what I should start working on. And yes, I have Heart of Thorns

So I bought this game back when it first came out, but eventually cut my time with it short since none of my friends had the game or a working pc at the time. Now everyone is on board and we all wanted to start a game together, but the problem is, is that I’m completely stuck on what class to pick. The game doesn’t seem to give a good representation of each class’ role. I definitely want to be a magic user (Elementalist, Mesmer, Necromancer), but I can’t get a good read on what one I should pick. I love magic and especially necromancy, so I figured I start as a necro, but a few people I know who have played the game told me they are completely useless in dungeons and raids. So i’m just wonder what the role is for each magic class, and which is the most beneficial for my team.