Overall, you seem to be attacking without first being strong yourself ( a habit that is easily indulged in on KGS without advese effects, I hear.
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20: Why push him northward toward your lone stone? Maybe C14 pushing him toward your wall?
25: He says that he is more worried about you playing D3 than attacking his left side group...
26:...but you do so anyway when much of the board is open.
27: This seems premature.
34: To seriously attack him on a board that is this open, you have to confine him. This is premature, and the wrong direction. You should play B8 here.
39: Now your D12 and E10 stones are virtually worthless, and he has D9 to challenge the influence of your wall.
40/42: If you have to pause to strengthen yourself after he makes the obvious reply to R8, then R8 was probably not the right move.
Maybe the simpler R13 would be better.
50/52: You owe a move at J5. This cannot end well.
54: Not only are you getting way thin, you are amost peeping at a bamboo joint. The shape move would be J6, taking the 4th point of his bamboo joint before he does.
64: Save K5 for a ko threat. Just play L6. He can't play K5 himself - it is too slow.
68: I agree: K10 would be better.
56: The overplay of B10 comes back to haunt you.
80: You don't have to kill his center stones; you just have to get out. I'd play O9. It has the threat of Q10.
82: Q10 doesn't seem to work here, for his natural reply of P9 weakens your big group.
116: J18 followed by H18 seems to reduce him to one eye, maybe has has a ko for life or has to run.