The graphics are totally corrupted and i can't see much, there's wrong pixels everywhere.
Any clue what is going wrong ?

Would be great to have some kind of answer as i can't play the game i bought.

As i can understand (i play Deponia only), there is common bug for Daedalic quests engine\config tool. Uncheck something in settings (texture compression?).
Although this is SHOULD be checked-on - this is bugged. But in some games and in some versions - fixed (or bugged back in next update).