You can't understand a formula without repeatedly applying it to great many problems, playing with it until you get a feel for how it behaves. Without that, you'll only be "understanding" your own imaginary version of a formula, a simulation in your mind with no grounding in reality.
Same with understanding anything else in life - you don't really understand anything until you get to the point you can, in your head, predict a specific outcome, test it, and be proven correct, repeatedly.
(At some point you may learn to gain robust understanding purely from simulating things in your head, deriving insight from lower-level principles. But this itself is a skill, a hard one, which few people master. It's not something a random kid, or adult, can do.)
Same with understanding anything else in life - you don't really understand anything until you get to the point you can, in your head, predict a specific outcome, test it, and be proven correct, repeatedly.
(At some point you may learn to gain robust understanding purely from simulating things in your head, deriving insight from lower-level principles. But this itself is a skill, a hard one, which few people master. It's not something a random kid, or adult, can do.)