So im lvl 13 now and had 4 quests where i had some problems.
I could solve all the problems with an easy trick.
90 % of the questproblems are missing items/npc or not reachable items.
That happens (mostly) when to many players are in the region and they server cant handle them right now.
1. To resolve the problem just log off but dont log in right away, wait 30 seconds, it can happen that you have to repeat that 2-3 times but it works.
But why wait 30 seconds? Because we play in different instances, that means just because the quest is broken right now in instance 1 doesnt mean its broken in instance 2 or 3. So the 30 second are there that your char is really logged of from the server and so its possible that they will put you in a different instance.
2. But there 're other things that you should consider, never log off directly on the spawning point of npc or items, that can lead also to questproblems.
3. Also rushing dialog options, can lead to not updating queststatus, to solve that let the npc atleast finish 2 words befor your skip to the next.
With this 3 little rules i could finish every quest till now.
I hope that this will help some people.