How do I change projectile properties when it collide with pickup items?

Well, I’m a beginner at UE4 and creating a game prototype where the player will be able to change the projectile when it collide with certain pickup items. But I can’t find a way to do that. I’ve tried to do it with some Var, but I can’t use the same Var in other blueprint. Can you guys help me? I’ve been trying to figure it out by myself, but I gave up.