There are different types of things that can happen in the opening. One of them is the classical development. Another is where tactics start happening early, and development and tactics intertwine so to speak.
This is a 3rd type where one side is allowed to make a big pawn center. Then the other side tries to break it down. (Black's move here were not a mistake.)
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Without analysis and experience it's not possible to judge moves when there are so many possibilities. If you've read a strategy book (like Pachman) then you'll have at least some kind of framework to judge moves. If that's true you could then try to do something like play guess the move with some high level games featuring an opening. Even write down some of your personal analysis and check it later. You could also try playing these openings yourself to get a better idea of what does and doesn't work.
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In any case, there's no cookie-cutter plan that makes one kind of opening play "correct" over all the others.
That said, classical development is much easier to understand. It's usually better to start with openings like that. This is another way to gain a foothold (so to speak) before trying to explore other approaches.
Sometimes I feel overwhelmed (usually in the opening) with the amount of options my opponent and sometimes I have in the game. With so many different choices which one is the correct or best one? This usually occurs when opening that don't involve a lot of pawn moves are played such as some Reti opening or Alekhine's defense or whatever this is just as a quick example. Are the moves correct? Should black be moving so many pawns etc.