What's with these "pointless" Opening moves?

I'm learning my first opening for Black and I was hoping someone could help me understand the move 11...Bb4. Opening Databases have it and the computer recommends it. Supposedly it is to guard against Qa5, but black promptly trades away this "defender" and White seems runs the Queen away as if they were never aware of the Qa5 idea. Black's move and White's reply seems so pointless.

(oops, after posting I see you're almost 1600 in daily, this answer is probably a little confusing, sorry about that. Learning openings 10+ moves deep is probably not the most important thing you could be doing right now)

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As a brief intro let's look at:

11...Bd6 12.Qa5.

Obviously Qxa7 is a big threat, so how will you defend it? 12...Kb8 loses a piece right away, and 12...a6 gives white the important b5 pawn break eventually. I hope you can understand that much without any other comment because the rest is a bit harder.

Before that though, I will say the engine backs you up that 13...f6 and 14. Qg3 are inaccurate. It says white should play 14.Qa5 and so black should play 13...Bd5. However there are a handful of GM games and none of them played this way, so it's useful to understand why. Here's what I think.

First let's look at the queen going to the queenside like you said:

13.bxc3 f6 14.Qa5 a6

Previously a6 was undesirable for black because of the b5 break, but now white has no b pawn. Meanwhile black has the idea of Bd5 + Qc6 which will force a pawn in front of white's king to move. So White may have thought the queen is off sides on a5. Both the opposite side castling and opposite color bishops point to the possibility of dangerous attacks on both kings, so white would rather the queen stay in contact with the kingside for defense, and judging Qa5 ineffective, would rather stay in contact with c7 for offense.

Second let's look at the queen not going to the queenside

13.bxc3 f6 14.Qg3

Now Bd5 + Qc6 doesn't force a pawn to move. For white's attack, let's imagine a setup like Qg3, Bf4, and Re1-e7... if at any time black's c pawn moves then suddenly sequences like d5 plus Bxa7 completely undermine the squares around black's king. For example b6 would no longer guard against an attack on the b file.

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This thinking by White turns out to be incorrect, because as black advances the pawns, the queen simply gets in the way and gives black tempo.

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Full game here https://www.chessgames.com/perl/chessgame?gid=1068203

So lastly let's see what the engine recommends

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Conclusion

So yes, both 13...f6 and 14.Qg3 are inaccurate.

This is a sharp position due to opposite side castling and opposite color bishops. One tempo can be the difference between winning and losing, and you see you have to be concrete, and that even GMs misjudge how to play.

Practical advice

Frankly, after move 10, I think you can end your opening prep there with the knowledge that "both players will try to attack the other's king as fast and forcefully as possible"

Sure you could memorize a few long lines from there, but your opponents are not masters, and so you'll likely never get to use those lines. In a real game both players are going to make a lot of mistakes after move 10... even if they're GMs as we just found out. It would be better to familiarize yourself with a few common patterns and general ideas after move 10 than memorizing any more lines.

For example in the Larsen game I show he offers to let white win a 2nd pawn with 15...g5 because he's trying to open lines to white's king.

One tip about opposite side castling is the player to make contact with their pawn storm first, or to start making threats first, is often objectively winning, practically winning, or both.

Thanks for the advice

I don't actually intend to remember more than 10 moves deep, but it is given, so I might as well look and learn from it. Being new I often don't know what to do once those 10 moves are over, so looking a bit further might give me an idea of where things are headed and how it plays out.

The explanation made sense, and not because of my rating  My daily rating is higher than it should be because I have only a few played games and got lucky during the big yearly tournament. My "lower-rated" friend is currently kicking my butt.

The position/situation can change in one move, the bishop defens a5, but when white is allowing getting doubled pawns, black better decides to chop it away and ruins white's pawnstructure.

When I learned chess, I also found those moves weird. But with more practicing, ur learning some things, like, in this example, to turn advantages (bishop pair here) into other ones. I hope this helped.

Yup, this is helping. Because I'm still a novice I just assume I'm missing something. That is why I'm asking here. Hopefully someday I will be the one explaining it to the confused noobie.

For me the key Black strategic move is 9..... Queen d7.

But I wonder that you learn opennings so deep...

I don't know what to do after first ten moves also... but as I understand that... maybe I am mistaking though... the players 2000+ know how to develop position... their pawns structure further. Further when first ten moves is done already.

I personaly know a few famous opennings on 3-5 moves deepness only.

The point of contention for me is 6. Qe2. Does white really want to trade? What about this instead?

6. Rxd7 is actually one of the lines shown (It's a Chessable Short & Sweet course)
I to feel like that is a more reasonable move, but I guess the point of a course like this is to prepare you for a few strange moves that you might encounter. Honestly, I'm trying harder to understand why they make the moves rather than remembering the order. when I play my <1000 blitz games we are likely to move out of the lines early on and I feel that then the why is all that matters.