Lots of Mistakes

There were lots of mistakes in this game. I am curious about this game. Why is move 18 a missed win? I don't see how moving the rook behind the bishop wins the game. Why does the chess engine say to move the bishop to d3? The black rook will just respond by moving the rook to d1 trapping the bishop and rook. I saw that move and did not do that because I did not want to trap my rook and bishop. As for the endgame that was terrible. I completely gave that away. Can I get some tips on the endgame? What is the best way to push a pawn with a king and rook vs king and rook? Why is move 77 for white a blunder? Is that for stalemate opportunities? Why is move 77 for black a mistake? Why does it say to move the rook to c2? White can just respond my wasting a turn by moving the rook. Why is move 73 a mistake? Why does it say to move the rook to f1? I will have no way to stop the checks if I do that. I am black.

Can I please get an analysis of this game?

The analysis likely flagged 18. Qc3+ as a missed win because it evaluated several alternatives as being better. There is no immediate forced win by checkmate etc.

Some observations about the position in question:

-Black's a8 Rook and Knight are sitting undeveloped on their original queenside squares.

-In order for Black's Bishop to be effective on b7, the a8-h1 diagonal needs to be opened, which will take time Black does not have. 

-White's a2-d5 pawn chain is pointing towards the kingside, suggesting White's play should focus on that side.

-The e-file is semi-open with an unprotected pawn on e7, so White would love to place a Rook on that file. Doubling Rooks on the e-file would be even better. Doubling Rooks with tempo might be possible with an eventual Re4 lift, forcing Black's Queen to vacate the f4 square.

-White's Bishop would control more squares if it were on the b1-h7 diagonal, where it would also be supported by the Queen to form a battery along that diagonal. Moving the Bishop also clears the semi-open e-file for the Rooks.

-A timely push of White's f-pawn to f4 (after Black's Queen vacates that square) is one possible way to increase White's spatial advantage further and initiate an attack on the kingside.

In a nutshell, while all of White's pieces are ready to pounce on Black's kingside with initiative, most of Black's pieces are misplaced on the queenside where there is no immediate counterplay. From a dynamic perspective, Black is effectively playing down material, but White has to act fast and not play passively.

So 18. Rae1 ... followed by 19. Bd3 ..., with the plan of doubling Rooks on the semi-open e-file, makes a lot of sense for White. Compare that plan with the position arising after 18. Qc3+ Qf6 19. Qxf6 exf6 (19... Kxf6 played in the game), and you will see White has thrown away the initiative and several positional pluses.

move 18 you did not take the knight with your Queen the engine counts that as a missed win as in you did not win a piece not the game. Of course you would have lost your Queen to the pawn on g2 if you had taken QxNf3. Engines for you.

Sorry it's late that should be Qxg3 followed by hxg3.

I am guessing you are joking about Black making an illegal move (18... Qxg3) while in check, but that's not even the move the OP is asking about. The OP is asking why the analysis flagged 18. Qc3+ as a missed win for White.

He is black in this game. Move 18 for white is not a missed win, it is flagged as an inaccuracy, nothing more. And he is describing moving a rook behind the bishop which is certainly couldn't be the move number 18, as he was in check and made a good move there.  I am not sure what move he is talking about.

White didn't have any missed wins in the game, black has 3 according to the analysis.

I realize the OP played Black in the game, but when they talk about the engine wanting to move a Rook behind a Bishop or a Bishop to d3 on move #18, they can only be referring to White's legal moves, not Black's. Although, having said that, I do find some of the wording in the question confusing, particularly "The black rook will just respond by moving the rook to d1 trapping the bishop and rook."

What looks really confusing now is the analysis did in fact flag 18. Qc3+ as a missed win for White at the time the OP posted their question. Since Chess.com's basic analysis at a depth of 18 is quite weak, I reran the analysis at a depth of 30 (premium membership) while drafting a reply, but I never looked at the results. It looks like the higher depth analysis overrode the one the OP ran and changed the evaluation of 18. Qc3+ from an missed win to an inaccuracy. I did not know rerunning an analysis of someone else's game at a higher depth overrides the saved analysis.

While writing this reply, I let the self-analysis run to a depth of 32 on the position. This time I checked it! Interestingly, 18. Qc3+ does not make it into the top five moves.