How can I be good at physics ? please help

When you fully understand the laws and definitions so you can recite them and make your younger sibling understand them, you then turn to describing those laws in shorthand. And that shorthand is of course all those equations. Math is just a shorthand language for precisely and accurately describing the laws of nature, the physics.

So, for example, when the conservation of momentum law says that "the sum of momenta before a collision will equal the sum of momenta after a collision" (and that's all it says by the way) you can translate the English into math shorthand. And SUM(p) = SUM(P) where p are the momenta before a collision and P are momenta after, is a start. And now you know what it means.

Once you can articulate the laws and their definitions, derive the equations found in your reading assignment. Don't memorize them, derive them using the physics you now know. Deriving what one needs is how real physicists do it. There are way fewer laws of nature to memorize than there are equations to explain them.