which is the hardest position to play in your opinion I think it is outside hitter and setter. What do you think?

My name is Armaan and I am from India. I am 13 year old. I was selected for under-14 state level but I miss that opportunity but now I am practicing more and trying to hit a spike but my vertical is very low therefore I can't hit a good spike. My height is 5.6 feet and I know it is not enough that is why I want to increase my vertical.