How would you interprete the word "unworldly" if you read it? Like 'an unworldly idea'.
Translated into my language it would mean what I want it to say, but im not sure about it in other languages.
So what does it mean?

Something not of this world, outside of what we know here on earth. Could be used when you exaggerate, saying that someone 'has an unworldly stench', or when something simply does not happen on earth like 'an unworldly landscape'.

I agree with Fantelle, but would add it has a suggested meaning of mystical/strange/weird.

Interesting, where I'm from "unworldly" would always mean "naive." Whereas I think what you're aiming at would be called "otherworldly," meaning spiritual/mystical/imaginary/alien.

[Ambiguity]

I've only heard of "worldly" be used to mean someone who is materialistic or non-spiritually minded, so I'd assume unworldly means the exact opposite.

Okay, I guess the word is the right one. Especially that Icyhands said "naive" and Peteman22 seid "weird". That nails down the meaning that I had in mind.