Hi i´m new at this game....
I´m in Gullicyk(don´t know how to spell it) and an halfling has asked me
to clear out some kobolds under the winery, but when a have gone throw the tunnel I se an mage but he turn invisebel direkly and harm great dammage is there any thing i can do? And is it nessesery?
/Calsiumus

It is Gullykin and the winery actually leads to the Firewine Dungeons.

This quest isn't absolutely necessary but you will get quite a bit of experience and a lot of good items from it (especially if you Pick Pocket a certain set of ghosts).

If you have TotSC installed, I suggest enabling the Pause on Enemy Sighted option under Gameplay - AutoPause. This will help out greatly.

The next thing to do would be to take just a single character down the stairs and case a fireball, throw a potion of explosions or firey burning against the opposite wall.

Another thing you could do is stealth your theif and give them Protection From Evil before going downstairs, immediately sneaking up behind the ogre-mage and backstabbing it. Then bring the rest of your party down to help in the attack.

The ogre-mage is quite easy so long as you don't let him get any spells off. Ranged weapons (especially darts) help out a lot here.