So this is the case, i unlocked the "jump over traps" challenge, and after trying it a few times with no success, it disappeared from my challenges list, I restarted the game and it came back, but the second time it also disappeared and now it doesn't get back when restarting.
I have also tried creating a new character, but the challenge is still missing and the marker to unlock it is now gone.

Thank you very much for your answer, i'll try it as soon as i have the time, it doesn't seem that difficult.
Again, thanks for guiding me to that post