It was indeed a "roller coaster of emotions", the problem was solved, then i spend some crystals to heal the party, and got 8/9 chest.
Did some math, couldnt advance more in that day, so i spent all i have (fight on arena, waterfall, and used some money), to my surprise in the next day, without opening a chest i got the mission done 0.o (probably duo to the mission being already active, it considered all the chests that i had already open, and a after a while it updated, idk).
The next mission was to fight 15 times on arena, as i fought in the arena the previous day(and already spent my crystals to heal the party), didnt qualify on top 3.
It is what it is, but yup, the problem as been solved.
Anyway thanks.