Guild Wars 2

I have tried three times now to do the defend the wall. Each time I have spent over 2o minutes each attempt and the zombies etc still attack. Why does it take so long? It now shows up that a new build is ready and will restart, Im like !!!!! Can anyone help please?

I always kill them relatively closely to the gate and never have to wait long

Are you standing inside the green circle indicated on the mini map? If you’re wandering out of the circle, that could be why it’s taking so long.