This is the explaination of the game I had during my game against @Zhigalko_Sergei. I am going to explain every move to enlighten the players about the moves I have played, the ideas behind them, and more. Hope this lessens the people who harrass me on my DM's. Here it is.
Game link if you want to check it out --> lichess.org/WO6QBqZY/black
1. e4 c6 - The caro-kann defense. The idea of c6 is to prepare d5, and when you play d5 immediately, there is a likelihood of getting your queen out early in the game and being very vulnerable.
2. d4 d5 - Both of the players take control of the center of the board.
3. e5 c5 - The idea of c5 is that when dxc5, white has a very awkward pawn positioned in the e5 square. The pawn structure of white would be broken too.
4. Nf3 cxd4 - The idea of cxd4 is to remove the defender of the e5 pawn.
5. Qxd4 Nc6 - The queen has recaptured the pawn in d4, and is in the center of the board and is gaining a lot of space, so Nc6 is a move to kick the queen out of the d4 square.
6. Qf4 e6 - now that the e5 pawn is weakened, the d5 pawn seems to have a single defender, which is the queen. When a trade on the d5 square happens, my queen is going to take up on that square and is going to be vulnerable to attacks and hence I would waste tempo.
7. Bd3 Nb4 - The white bishop is activated, and it has to be neutralized. The idea of Nb4 is to take the Bishop on d3, to remove an active piece and on the other hand destroying the pawn structure.
8. O-O Nxd3 - Executing the plan from move 7.
9. cxd3 Ne7 - The idea of Ne7 is to keep an eye to jump on the f5 square. Also muti-purposed as it can also jump to g6 and gain tempo attacking the queen.
10. Nc3 Ng6 - I chose Ng6 instead of Nf5 because Nf5 is a bit of a passive move. Ng6 gains me tempo.
11. Qg3 Be7 - Making room for my king to castle and at the same time, if the Knight on f3 moves, Bh4 is always ready.
12. Ne2 Bd7 - Developing my light squared bishop, and also making room for my rook to be on c8 to be on an open file. My rook would be very comfortable and active on that square.
13. Ned4 O-O - Moving my king to safety and it is a thing to do after developing your pieces.
14. Bd2 Rc8 - Taking on an open file
15. a3 f6 - the idea of f6 is It was a pawn break to open up the position;
f6 is to also get rid of the e5 pawn in the center of the board;
It has overextended and thus an easy target;
Can you find another move to target the e5 pawn? no. That is why f6 is the best move. Human-wise or computer-wise. This is the move that brought suspicion to some players, that I have to clear up what this move does.
16. Rfe1 fxe5 - taking the lone e5 pawn. opening up my f file for my rook on f8, and gaining almost full access on the center of the board.
17. Nxe5 Bh4 - The knight on f3 moved, and the plan on move 11 should be carried on.
18. Qg4 Bxf2+ - The queen is pinned to the f2 square, which f2 is kept-eye on by my rook on f8 and Bishop on h4. Bxf2 forks the king and the rook.
19. Kh1 Bxe1 - Taking the rook after the fork.
20. Nxd7 Rf1# - There was no piece guarding the f1 square, because the rook should have been guarding it, but the bishop is blocking it from e1, and hence Rf1 is a back-rank checkmate.
Game link if you want to check it out --> lichess.org/WO6QBqZY/black
1. e4 c6 - The caro-kann defense. The idea of c6 is to prepare d5, and when you play d5 immediately, there is a likelihood of getting your queen out early in the game and being very vulnerable.
2. d4 d5 - Both of the players take control of the center of the board.
3. e5 c5 - The idea of c5 is that when dxc5, white has a very awkward pawn positioned in the e5 square. The pawn structure of white would be broken too.
4. Nf3 cxd4 - The idea of cxd4 is to remove the defender of the e5 pawn.
5. Qxd4 Nc6 - The queen has recaptured the pawn in d4, and is in the center of the board and is gaining a lot of space, so Nc6 is a move to kick the queen out of the d4 square.
6. Qf4 e6 - now that the e5 pawn is weakened, the d5 pawn seems to have a single defender, which is the queen. When a trade on the d5 square happens, my queen is going to take up on that square and is going to be vulnerable to attacks and hence I would waste tempo.
7. Bd3 Nb4 - The white bishop is activated, and it has to be neutralized. The idea of Nb4 is to take the Bishop on d3, to remove an active piece and on the other hand destroying the pawn structure.
8. O-O Nxd3 - Executing the plan from move 7.
9. cxd3 Ne7 - The idea of Ne7 is to keep an eye to jump on the f5 square. Also muti-purposed as it can also jump to g6 and gain tempo attacking the queen.
10. Nc3 Ng6 - I chose Ng6 instead of Nf5 because Nf5 is a bit of a passive move. Ng6 gains me tempo.
11. Qg3 Be7 - Making room for my king to castle and at the same time, if the Knight on f3 moves, Bh4 is always ready.
12. Ne2 Bd7 - Developing my light squared bishop, and also making room for my rook to be on c8 to be on an open file. My rook would be very comfortable and active on that square.
13. Ned4 O-O - Moving my king to safety and it is a thing to do after developing your pieces.
14. Bd2 Rc8 - Taking on an open file
15. a3 f6 - the idea of f6 is It was a pawn break to open up the position;
f6 is to also get rid of the e5 pawn in the center of the board;
It has overextended and thus an easy target;
Can you find another move to target the e5 pawn? no. That is why f6 is the best move. Human-wise or computer-wise. This is the move that brought suspicion to some players, that I have to clear up what this move does.
16. Rfe1 fxe5 - taking the lone e5 pawn. opening up my f file for my rook on f8, and gaining almost full access on the center of the board.
17. Nxe5 Bh4 - The knight on f3 moved, and the plan on move 11 should be carried on.
18. Qg4 Bxf2+ - The queen is pinned to the f2 square, which f2 is kept-eye on by my rook on f8 and Bishop on h4. Bxf2 forks the king and the rook.
19. Kh1 Bxe1 - Taking the rook after the fork.
20. Nxd7 Rf1# - There was no piece guarding the f1 square, because the rook should have been guarding it, but the bishop is blocking it from e1, and hence Rf1 is a back-rank checkmate.