I lost XP if i lose a challenge ?

Answer 1

Yes. There is a negative fall and you lose your XP for losing the challenges. Its better to take your challenges seriously and learn from your mistakes.

Answer 2

You don't necessarily loose XP when losing a challenge.
If you challenge someone with much more XP than you in a language, then you only loose 1XP by failing the challenge.
On the other hand you get 1XP per right answer, so if you have more than one right, you will actually win XP!!!

Answer 3

absolutely