Before you become something, you can use either verb. The point is that becoming something is a single action, and being something is the state that it brings about.
Yes, you are correct, and it also works as a linking verb
They became best friends," the word became links the subject (they) with information...
Is that right?
Thanks for your answer I .understand your point of view.
To become indicates a [process of] change - from something to something else: you are now a bus driver, but you want to change into being an astronaut.
The sun shone and the ice became water / As he got older, he became forgetful
To be ignores any change and describes a state -> The ice is now water. He is forgetful.