I beat a strong Grandmaster in 23 moves

Yeah, of course, everything up to move 12 was well known theory, although my 10.. Re2 is not the mainline (although it is inspired by Game 4 of the Carlsen - Karjakin 2016 World Championship match). 4.. Nxe4 is the main move and the opening (Berlin Defence) is extremely well known and practiced by players of all levels including the highest level.

It is a 3+0 blitz game...
Why 12...Nf5 instead pf the centralising 12...Ne4?
Why 13...d5 blocking the diagonal pf hjis own Bb7? He will then re-rout his fianchetto bishop Bc8 and Bg4. That cannot be right.

@TrappedPiece huh?? I'm perfectly aware the mainline is 3...a6, I said Nxe4 was the best move on move 4 after 3...Nf6 is already played.

No 3...Nf6 is main line now, thanks to Kramnik.

@tpr yes this is also true. I'm just very confused about what @TrappedPiece is saying, it seems he was implying that he agrees with the guy who thinks the Berlin is bad?

@soni777new I do not believe @TrappedPiece meant to say that the Berlin is bad, I understand he believes this variation not to be the main line, though recently it has become the main line with Karjakin playing it repeatedly.
Both Kasparov and Kramnik believed the Berlin to be bad. Kasparov sought in vain for a refutation when Kramnik played it against him. Kramnik described his Berlin games against Kasparov as self inflicted torture.
Lasker played it in his time and believed 3...a6 to be loss of tempo. As white Lasker answered 3...a6 with 4 Bxc6 which he considered a refutation of the Ruy Lopez.
Opinions shift over time...
Nobody knows anything for sure about openings.

@tpr OK, thanks.

@tpr Raises very good points. I think that both 12.. Nf5 and 13.. d5 were autopilot moves, which are typical for this line, yes, but not with the bishop on b7. They are typical in the normal lines where ..Re2 and ..b6 are not included. He seemingly didn't have enough experience with this subline of the Re1 Berlin to understand such subtleties.

Yes, that will be it. 10...Nf5 is a regular move. The whole point of 10...b6 and 11...Bb7 is to enable 12...Ne4. Maybe he was experimenting with an opening he is not used to play.

Probably 10..Re2 threw him off a little. He remembered the Carlsen - Karjakin game which made the move famous, and he remembered that Karjakin's reply was ..b6 but after that he didn't know much more about the position. Or that is what I would expect.