How is the normal difficulty in this game? challenging enough?
Should i play it on hard difficulty for the first play through?
Im a little worried that with those abilities that you acquire you can be a little bit overpowered...

Is there any other tips you would like to share with me before starting the playthrough?
Change something in the settings maybe that i didnt notice?
there are really lots of options in this game.

Thank you all for your help.

Honestly, I think Very Hard is the way to go. Sure, you die in 2 hits, but just don't engage people in direct combat,
and don't be seen.

I am from the EU, so haven't got the game yet, but a mate of mine has thrown a few tips my way.
Normal will be a challenge in itself for regular players, but if you've played Thief 1 and 2, or Deus Ex or Splinter Cell etc.
Then you're used to try and stay hidden, therefore go for Hard or Very Hard difficulty, as it would punish you more for being spotted and therefore make it harder to get out of a sticky stuation.
Always keep your eyes open about different approaches to an objective or to killing/knocking out a guard.
Exploring is a must to really get the depth of the game, so explore the areas and find the runes and bone charms with the heart.
and as my mate said, this ain't "Infamous" or any superhero game, just because you have powers, you aren't a superhero.
You won't be overpowered, as using your skills will drain your mana easily and you'll be without anything at all.
So the skills are used in sticky situations and not used as spam.

Well that's all he told me so far ^^

normal is a good choice for starting out

Really, it's impossible to make a recommendation to the OP without knowing something about their experience with stealth games, playstyle, and whether they enjoy challenge or get frustrated easily These choices really depend on the player.

I'd say try the starting mission on normal; you'll find out within a couple of rooms whether you're reloading a lot or gliding through like a ghost.

At least hard. The harder difficulties force you to explore and be methodical, which ends up being a lot more rewarding.