Hmm. This’ll be a 4k-level commentary.
Well, first of all it’s a two-stone game so you can afford to play a bit slackly, softly, or slowly at times.
Your joseki (4–6) was fine.
(8) O17, enclosing the corner, was perfectly OK.
Note sure why you approached high with (10) O4. That way of play loses territory in comparison to the usual “low” approach O3. Instead of an immediate extension (12) K4, you should define the position with the underattachment Q3, continuing into Play Go at online-go.com! | OGS having that discussion immediately allows you to define your shape and limit the extent of the corner.
The kick (14) was not at all bad, but I wouldn’t find it the most appropriate joseki for that part of the board. Did you consider a pincer? Perhaps with the idea of playing like Play Go at online-go.com! | OGS?
As said, (18) C11 is not a good-looking move – it’s a sort of play called the armpit hit. The armpit hit isn’t always bad, but should usually be regarded for application in settling weak groups.
(20) R13 is reasonable. At this time, though, you could consider asking at L17, gesturing at the defects in White’s top-side shape.
White’s shape after (29) can be made into a ko with the atari T16+. If White connects with (31) S17, you play Q18+ and kill. If he instead plays (31) T18 you, again, play Q18+ and kill. White’s strongest resistance is (31) Q18, but that shape can still be killed outright with Q19, playing on the point of eye division. After (30) T16+, White is obliged to defend the ko with (31) T17.
(36) N14 is overconcentrated. Consider instead such moves as L14, R8, R3, Q3, and even tengen.
(38) O15 was too passive. Since White contacted your stone, you can push against the intruder with M14 and in doing so make influence into the centre. In the game, White is happy to take that point himself.
Nice job finding the ko on (40). And especially the equally accurate T18! (46) R18 was unnecessary, though,
(48) P8 was a natural response to White’s central posture. (52) E8 was also a good spot.
I think you’d find it interesting to consider the upward push (54) F5, which is a bit more spirited than G4. However, being “forced” to take fourth-line territory is rarely a bad thing.
You definitely owed a move in the centre at (56). Where exactly that move should have been is above my level, but the keima looks OK.
Atter White tenukis with (59), which perhaps he shouldn’t have done, the situation immediately becomes very tactical, especially to regard to the cut in White’s group around E5. After White finished defending the upper centre, I would’ve wanted to take that cut at (72), especially since Black B10 was lingering in the position. L9 was endgame or even almost dame, not confronting White.
Still, my feeling at (76) is that White’s win condition is to kill your central group. That’s why I would’ve likely abandoned the P8 stone (which is only a single stone, after all) and tried to begin connecting back to the bottom side. Connecting properly isn’t a simple matter tactically. L6 looks best to me.
(81-2) E10–D11 is a painful exchange for you, even though it makes an eye, because it removes the aforementioned B10 cut. That B10 cut, separating the H10 group from the walls of the upper-centre moyo, is a very important tactic. With the removal of that aji, the game looks to slip into yose; even though that is where the game was decided, it’s not something I want to review.