later stages of the game is really bad play, so i'd like to hear opinions on the opening moves and what should have been played at black move 63. thanks

Are you black or white?

i was black

B11: It's not that bad, but if you want to play on this side probably it's better to play in the middle of the gap at c10. One reason is if white plays c9 now you want to extend to c14, but then if white plays c15 kick you stand at d14 to make a 2 stone wall, but now c11 is only 2 spaces away and you'd prefer to make a 3 space extension from a 2 stone wall. If c11 was at c10 it would be the perfect 3 spaces so white probably won't kick. You might worry that if you play c10, then white c8, and then after c14 white comes in the gap at c12, but as the e14 jump is 99% sente (white answers at f16 or f17) you can then play d11 to surround the c12 invader. Also as you played 4th line at q6 another good idea is to add a move at r10 to prevent annoying r8, this also is a nice extension from your shimari at the top right.
B15: Hmm complicated making more groups. Easier ideas are simply take corner at c3, or split at e6.
W16: But this is not good as white separates his own stones, d6 would make a strong shape instead.
B17: Good
W18: Bad again
B19: Good, white is hurting himself, just keep splitting him.
B21: This is off topic, there is still fighting going on at the lower side, white could play f4 to separate your stones, so f5 would be a good idea to join yours together and also surround white's corner which could be in danger next. So white should add a move to his corner which means you get to surround and (almost) connect in sente which is brilliant for you! Locally it's good though.
B23: Another reasonable local move, but again lower left is urgent
W24: Strange but not so easy to answer. Imagine if you already had f5, then e5 d5 and e7 ladder would be awesome for you.
B25: How about d5, aiming at e5 or c4? In the game you capture only c7 which was small and white cut off f3 and made a strong shape.
B31: You don't need this move (and it helps white on the outside), you are already connected thanks to b7.
B33: This kind of armpit hit is usually bad as you make white have a strong shape and you have not many liberties. Maybe d2
W36: White could think about e3
B37: Good to make base
W 56: small
B61: Now that white has a strong shape taking a liberty isn't so powerful, so jump ahead at n13
B63: White is threatening to cut off r9 with r8, so good idea to defend that at q8. Black seems ahead. You could practice counting on this position.

thanks for your time guys