Can you help me,
for example, I have in the scene several spheres,
how I can count in BP how many spheres I have when start the level,
and how many spheres I had pickup.
you can use “get all actors” or other related solutions like “has tag” described there : https://docs.unrealengine.com/latest/INT/Gameplay/HowTo/FindingActors/Blueprints/index.html. To know how much element, on each loop body you do “number” (an integer variable) = number + 1, on completed you have your “number” of actors in level. And for pick-up, you use another integer variable"picked-up" and you add 1 each time you pick-up an item (as you may need different pick-up you may need an array of variables)