I hope it's not 3 days. That would take forever @_@

I assume reading this:

"Inmunity" (inmunity challenges)
Each day change one tribe will be the looser tribe. The looser tribe will have to do the immunity challenge (the better your water/food levels the more time you will have). The best participant will avoid being evicted. Looser tribe members may vote out one participant.

-
It's every 12 hours.

That makes it sound like 3 Days.

Day 1 - Tribe Immunity Challenges
Day 2 - Loosing Tribe Immunity Challenges
Day 3 - Someone voted out

I think it's 3 tengaged days so 1 day and a half

every 12 hours.