If you are taking action, studying hard and not overloading, then your studies will naturally get better. It’s important to be taking action and not simply waiting for “brain tingles” or some other random phenomenon - that is not anything worthy of note.
The way to see if it works is to actually take action, study well and then as you do so you’ll see the changes happen. This is the most common mistake with intelligence and studying related subliminals - waiting for some kind of magical “I know it all” moment, when it is a gradual unfolding.