Four of your six mistakes moved a piece that was defending something.
A fifth handed White a check instead. In four of those five positions the engine's move gives up nothing at all, no loose pawn and no check offered, and the exception is the last one, where its move hands over a check on the way to forcing mate.
13...Qb6 -- the queen stops covering d6
Fourteen seconds, and -2.0 became +0.0. The queen on d8 was defending the bishop on d6, and from b6 she cannot: White's own knight on c6 stands between her and it along the sixth rank.
Qc7 kept the job and the advantage. Qc7 Bxf6 gxf6 Qg4+ Kh8 Qd4 Rg8 Qxf6+ Rg7 Nd4 holds -1.9, and it is worth setting that against what actually followed, Bxf6 gxf6 Qg4+ Kh8 Qh4 Rg8 Qxf6+ Rg7 O-O-O Qc7. The first four moves are identical and the queen reaches c7 in both. The version where she went there at once is nearly two pawns better.
The engine rated every alternative to Qc7 at least 1.6 worse, so this was not a position offering you options. Neither was 16...Be6 three moves later, where the push d4 stood 2.2 clear of everything else and you played it one move afterwards anyway.
19...f5 -- e5 loses its defender, and White gets a check
Thirty seconds at -2.5, and you pushed to hit the knight on e4. The pawn on f6 was doing two jobs you needed: defending e5, and denying White a check on the g-file. One move gave up both.
Qg3+ Kh8 Qxe5+ f6 Qxd4 Qc7 Nec5 Bxb3 Nxb3 Rg8 is the engine's line, and its first three moves are the whole mechanism. The check comes up the open g-file. The recapture on e5 then arrives with check as well, because the king has just been driven to h8 and h8 is on the long diagonal. The d4 pawn follows for free, since the knight on b3 covers that square. Two pawns, and -2.5 became +1.9.
Kh8 was the move: Kh8 Nec5 f5 Nxe6 fxe6 Qd3 Bf6 f3 Rg8 Kh1 keeps -2.1. Read what is inside it. You still get to play f5, two moves later, once the check it would have allowed no longer exists.
22...Rg8 -- four seconds, and 23.Qf6+ collects e5
After 21.Ng5 you stood at -3.1, with e5 still undefended from three moves earlier. Four seconds went into 22...Rg8, and 23.Qf6+ was the answer.
f6 was the move: f6 Qh4 Rac8 Nc1 Bd5 Nd3 Rg8 f3 Rxc2 Rf2 holds -2.7. The pawn puts a defender back on e5 and takes f6 away from the white queen in one go, and Rg8 still turns up in that line four moves later, at a point where it costs nothing. What you got instead was Qf6+ Rg7 Qxe5 Rg8 Nxd4 f6 Qxe6 Rxg2+ Kh1 Qxd4, level at +0.0: the rook goes to g8, is checked back to g7, and returns to g8 having achieved nothing while two pawns walk off.
Four seconds is the number to sit with. The position asked one question, and there was no time in which you could have asked it.
25...Qxc2 -- the same idea, pointed the right way
25.f3 left the pawn on c2 loose and you took it immediately. What makes that winning rather than a pawn grab is the thing you saw: c2 was the only defender of the knight on b3. Qxc2 Rf2 Qxb3 Qxd4 a5 Rd1 a4 Rd3 Qc4 Qe3 Qh4 is the continuation, and you played its first three moves exactly. White's rook has to come to f2 to block the second rank against your queen, and that is what leaves b3 hanging.
This is your best move of the game, and it is the review in reverse: you won a piece by asking what a pawn was defending. One move earlier, 24...Qc6 is the same question left unasked. It stopped defending d4 and left the pawn loose, +0.0 became +2.0 in twenty seconds, and Rd8 and d3 were both exactly equal at the time.
32...Qf2 -- the mating move, five moves early
You had mate in five. Rxg2 Qd8+ Kh7 Qg8+ Rxg8 Rd1 Rg1+ Kh2 Qf2# is the line, and the last move of it is the move you played first. On move 32 the queen on e3 was the only thing defending h6, so 32...Qf2 gave up the pawn and handed over 33.Qxh6+, turning -#5 into -5.5.
You were still winning and you finished the game. The point is that thirty-six seconds went into moving a queen without asking what she was holding, in a position where you were already mating.
What to drill next
- The position after 19.Qf3. Beat the engine from here three times running. You are at -2.5, and the move that keeps it is a king step that gives White nothing.
- Capture the defender. This is 25...Qxc2 as a puzzle theme, on repeat. You read the board this way well when the loose defender is theirs, and the drill is worth doing precisely because it is the same reading, aimed the other way.
- Hanging pieces. Four of your flagged moves gave up a defender, and twice the thing it was defending was then simply loose. Finding that in a puzzle is the cheap rehearsal for finding it in your own position.
Before you move a piece, name what it was defending.