You did quite well in the opening, before things got too complicated. Then you lost after picking a difficult fight against an opponent 8 stones stronger than you

. The best advice for a high handicap game like this is to find ways of avoiding such fights. Fight where you have a big advantage, but look for ways to compromise elsewhere. Some more specific comments:
Move 28 could push once more at G12, before going back to capture at B13. Since you know the left side will be completely safe after B13, there is no harm in pushing W that way, and it strengthens your weaker group considerably.
The attachment at move 44 helps W strengthen his weak stone. If W simply stood up at O16, were you planning to cut around N15? That seems unreasonable. So better just to extend around R14, without provoking W to strengthen himself. Or consider a slow but solid good shape move like M17, eliminating any opportunities for W to cause trouble around here.
Move 50 is a do-or-die move which actually captures W, but if it did not, the game would be over. Consider compromising with the J18 nose tesuji. This allows W to capture one stone, but then B gets to squeeze and live easily, for a reasonable result.
Move 60 is good, avoiding a difficult fight. But then B should follow-up at move 62 with the tesuji Q18, giving up the P17 stone to secure the corner. Move 66 is absolutely needed, to stabilize this group; nothing else on the board comes close in importance to this.
Up to move 66, B has actually done quite well. Territory is fairly even, but B still has 4-5 handicap stones of extra thickness.
The game fell apart after the LL corner invasion. B deliberately provoked a very difficult fight up to move 103, passing up several opportunities to get a simpler good result. At move 104, it is still not too late to block at C9, which I guess was your original intention, when you thought it captured W. But look a little deeper, this is still a great move -- it gets a perfect squeeze, forcing W to capture 3 stones in gote, while making immense outside thickness. Try playing this sequence out, then step back and look at the whole board. Do you really need to try for something better than that?