Heroes 4 question (spoiler)

I’ve just got Heroes 4 and have finished a few easy maps. So I thought I’d tackle a campaign, and started with the Barbarian one.

But I can’t get to the nearby town until I find the artefact ‘cart of ore’. So I can’t hire a new hero.
I can’t get thru the archway either.
Pirates guard the shipyard.

I managed to clear the ‘centaur recruitment’ sites (and of course there are some beserkers available).

But my hero keeps dying (especially when I tackle the ‘nomad recruitment’ site).
This ends the scenario.

What am I doing wrong?
What should I do?

Your help will be appreciated!

Hey, come on people!

If I want to know something obscure about e.g. a film, I get an answer in 2 minutes or so.

Hasn’t anyone done this campaign?