When I talk to Darmus, he talks about the portal, unfortunately when I click on the portal I get a message that it cannot be used, how to solve this problem?

haha, your not that FAST.
its a quest line, starts at the tavern. then the wizard.
you gotta click at the trees, diliver the small pearls.. read the dialogs

I know, I completed the quest in the tavern and in the quest log I have to talk to Daramus, he talks about the portal, but nothing new appears in the quest log and the portal itself does not work.

what trees specifically, I clicked through all the dead trees under the portal, where there are evil eyes and cursed eyes.

theres 2 dead trees with a very dark sparkling.
1 at the middle settlement of the wildgling island, 1 at the north corridor in the werewolf cave.

Thanks you bro ;]