I just through that i could use 2 Array in sync, one to keep the information of “buff and debuff” and the other one to contain the time remaining that i update each second, in a loop on my event graph that update stats, when it reaches zero i remove the index in both array. It would work i think but i hoped to find a cleaner solution.
Like something that i could launch on the character an infinite amount oftime that have its own timer and affect stat in a certain way until it reaches zero. 
Anyone got any idea ?