First of all realize that if White had connected at G6 instead of effectively passing at 244, White would have been 2 points better off. If play continued as in the game, but White did not give Black a free point by throwing in at M7 as a ko "threat" in a half point ko (face palm!), White would have won by half a point. So one of the main things that went wrong was Black's assessment of the position. Far from being well ahead, he was probably behind.
In general, however, Black failed to make make territory from the stones played. An excellent example was the invasion of Black 47. What did Black want to achieve here? Before the invasion there is a weak White group at the top and a wide White extension along the right. As a result of the invasion, White's weak group at the top links up to a new White wall in the center, making it safe. Meanwhile Black's new wall in the center accomplishes... not much. Black never finds a way to play against White's position in the lower right. It is too strong to kill. So Black's original invasion was suspect. Black's invasion stone and White's lone stone were both weak. In fact though, the White stone had somewhere to run to and in the process helped White a lot. Meanwhile, for all the sound and fury, Black really did not have a use for the invader once White's right side and top stones linked up.
Black has to learn to play more strategically and think more about where the territory is going to finally come from. It is not enough to continuously chase each other around the board. Although attacking is a huge part of Go, in the end it is a game of territory.
. To which you replied at "a".
is correct. Now Black has 9 pts. in the corner. You ended up with 5.