I have a few questions. First off: I'm level 8 currently, and the only quest that I still have is the one regarding the ship and the mailbox. How are people getting to level 10/11 to fight the Kayran?

Also where can I acquire the formulae for the Kayran trap?

Leveling, perhaps by killing monsters in the woods repeatedly. Meditate to start a new day, go kill. Repeat.

Cedric has the trap diagram.

You don't need it to finish the fight. It just speeds it up a tiny amount.

Your level doesn't meter because when you fight the Kayran you use Yrden Sign. Just invest the points in vitality and defense. If you want to lvl up then check out the billboard for monster slaying contracts. Moreover, you can look for quest around the town and inside the inn for Gambling quest (Poker face), fist fighting quest and an arm wrestling quest. If you need the formula for the trap then buy it from Cedric (as mantioned above me). Good luck ^^

Might be just me but I thought the mobs and the sneaky endregas in the forest are more dangerous than the Kayran (once you learn the latter's pattern). I thought level 7/8 is sufficient to fight the Kayran, you just have to be careful.

Would be helpful if you tell us what side quests you completed if you still want to level up.

LOL you are right, fighting mobs in the forest is harder than taking down the Kayran XD but after he'll complete the nekker and endegra contrcats he will be able to arrange there field trips for kids. BTW, it doesn't really meter if you are lvl 8 or 12 because when the Kayran hits you you will die in 2 hits (If you are lucky).

I've completed all the side quests I can find. And thanks for the trap location.

What I mean is what are the names of side quests you have completed? Anyway here is a list
a) Troll
b) Nekker contract
c) Endrega contract
d) Malena
e) Fight club
f) Poker dice
g) Little shop of dreams
h) Something else with the incense shop
i) Claws of madness
j) Arm wrestling
k) Royal mailbox.
l) Hung over

Might have missed a few. You can also meet up with Loredo prior to killing the Kayran.

Ive done all of those except Malena and Hung Over, and i need to find the 2nd ship for Royal Mailbox

Nice. The 2nd ship is in the next act. Now go kill the Kayran hehe!

Well where do I pick up Hung Over and Melena? Or are they after the kayran?

The Malena quest is picked up when you interrupt some people in the village right outside of Flotsam who are arguing with an elf woman, and the hung over quest... I honestly don't know what triggers it, but if you occasionally visit the Blue Stripes quarters in the building next to the inn you'll wind up in the middle of a party and end up getting it.