It was crashing when I changed This:
PickupMesh->OnComponentBeginOverlap.AddDynamic(this,AAPickup::OnActorEnterPickupBox);
To this:
PickupMesh->OnComponentBeginOverlap.AddDynamic(this,&AAPickup::OnActorEnterPickupBox);
And when I dragged the mesh in it crashed. it happened 4 times .i would like your help.