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I found a Celtic song I really loved but of course not speaking Celtic I didn't understand a word of it. I finally looked it up and it turned out to be a recitation of the menu at a wedding feast. It was the language that seemed complex to me but was actually expressing simple facts.
The mathematics used in Einsteins equations are complex but it is a complex language to express and predict very precisely and unambiguously the implications of certain simple ideas. However compared to the common language (be it Celtic, French, English or Espranto) used to express the subtleties of marriage, love, food, and life, to express it in multiple ways so that the author can choose the way that best fits into the rhyme and meter of a song or poem, ... compared to that the mathematical language used in Einstein's notebooks is actually quite simple. It is just a foreign language and so like Egyptian hieroglyphs it may look more complex than it actually is.
If you are interested then by all means begin to study that language. Start with your school algebra and geometry.