Well, first, one needs to start with Sir Isaac Newton's Principia Mathematica. Then, once one has mastered that, then move on to Einstein's General Theory of Relativity and Special Theory of Relativity, etc.
So, let's start with Newton.
"A look at Isaac Newton's Principia Mathematica (Mathematical Principles of Natural Philosophy). This great physics book first published in 1687 contains Newton's laws of motion and includes work on the motion of bodies including the inverse square law. " YouTube channel: Tibees