How can i destroy a wall if for example i shot it 4 times?
Make a Blueprint called BP_Wall. Add a StaticMeshComponent for the wall, and then select it. Go to the details panel, scroll to the bottom, and add an OnComponentHit event. Add a variable called hits, and set it to 0. Every time your OnComponentHit event is called, add 1 to the hits variable, and check if it is greater than or equal to 4. If so, called the DestroyActor function to destroy the wall and remove it from the world.