Understanding the tech tree and game flow

I used to play AoE in my youth, though all I did was “E=mc2 trooper” and watch everyone burn 11

Now that I’m older and more serious, I bought the Definitive Edition thinking that having spent a year playing AoE2 I should be quite ready. I was right, but not right at the same time lol

So, um, anyone willing to help me out with reading the tech trees and understanding the units and strategies? Thank you very much in advance