Guild Wars 2

I mean Are the goals can be achieved with two or more players? If a player succeeds, Do others get the achievement?

No. They are done independently

JRM.6218:

I mean Are the goals can be achieved with two or more players? If a player succeeds, Do others get the achievement?

That would simply encourage one person to sell gold adventures and other to just sit afk
Like how we have our dungeons -_-

Thanks for answering.

So, Do the adventures are more personal than Personal Story?

Adventures can only be progressed individually. Most of them take place in the open world with other players around, but a few are completely instanced. For the open world adventures, other players can either be a boon or a burden. Multiple players in the salvage pit for example are going to create a mess with the tendrils throwing AoEs everywhere, plus dead players can easily grief you when you need to interact with things. I’ve never seen it personally, but I heard you could cheat with the help of other players by, for example, using a Mesmer’s portal.