How Goku Achieved Super Saiyan 3

The final transformation in dragon ball Z was achieved off-screen but how did Goku achieve the highest level of Saiyan power?
I have a theory and it is deeper than you think
Music by: MokkaMusic / Run Faster

[@chaganshanker3584]

Let's go that is not too bad 👍

[@anthonyhernandez1767]

cant understand u

[@Lateninetieskid]

I'll be more clearly next time