Your SGF is truncated, here is the full one from the kgs archives.
(;CA[utf-8]FF[4]ST[2]RU[Japanese]OT[5x30 byo-yomi]C[sadperson [8k]: hi
tictac [8k]: hi gg
]
AP[CGoban:3]SZ[19]GM[1]DT[2011-05-17]PC[The KGS Go Server at
http://www.gokgs.com/]
PB[tictac]BR[8k]PW[sadperson]WR[8k]KM[6.5]TM[1200]RE[W+15.50]MULTIGOGM[1]
;B[pd]BL[1191.9];W[dq]WL[1198.33];B[pq]BL[1176.6];W[cd]WL[1194.26];B[qk]BL[1172.39]
;W[po]WL[1191.94];B[np]BL[1168.8];W[qq]WL[1184.39];B[qr]BL[1161.36];W[no]WL[1182.45]
;B[qp]BL[1138.67];W[rq]WL[1178.24];B[pp]BL[1132.89];W[qo]WL[1172.2];B[oo]BL[1123.2]
;W[on]WL[1169.67];B[op]BL[1121.92];W[rp]WL[1168.94];B[nn]BL[1116.3];W[nm]WL[1166.48]
;B[mo]BL[1113.53];W[om]WL[1165.57];B[qm]BL[1102.73];W[pl]WL[1163.79];B[ql]BL[1096.21]
;W[pk]WL[1155.29];B[pj]BL[1090.44];W[oj]WL[1145.73];B[pn]BL[1073.37];W[rn]WL[1142.53]
;B[qn]BL[1065.32];W[ro]WL[1138.88];B[pi]BL[1061.49];W[rr]WL[1137.46];B[pr]BL[1056.84]
;W[rm]WL[1117.42];B[rl]BL[1051.96];W[rs]WL[1108.91];B[mm]BL[1036.1];W[nk]WL[1102.33]
;B[oi]BL[1031.88];W[ni]WL[1100.58];B[nh]BL[1027.35];W[ml]WL[1099.63];B[ll]BL[1022.27]
;W[lm]WL[1097.9];B[mn]BL[1019.11];W[lk]WL[1097.2];B[kl]BL[1016.4];W[mi]WL[1087.36]
;B[mh]BL[1011.56];W[jd]WL[1076.14];B[do]BL[996.046];W[co]WL[1064.54];B[cn]BL[935.269]
;W[cp]WL[1061.05];B[dm]BL[918.499];W[fq]WL[1055.35];B[ci]BL[894.697];W[cg]WL[1050.63]
;B[eh]BL[890.01];W[cl]WL[1037.7];B[dl]BL[882.991];W[bn]WL[1035.87];B[cm]BL[873.605]
;W[bl]WL[1026.85];B[bm]BL[868.659];W[am]WL[1025.68];B[bo]BL[865.387];W[an]WL[1024.34]
;B[bp]BL[858.393];W[bq]WL[1022.45];B[dp]BL[854.035];W[cq]WL[1020.96];B[eq]BL[847.71]
;W[ep]WL[1009.3];B[er]BL[844.843];W[fr]WL[1006.88];B[eo]BL[831.465];W[fp]WL[1005.32]
;B[ck]BL[826.758];W[bk]WL[980.894];B[bj]BL[822.407];W[dk]WL[979.972];B[cj]BL[818.057]
;W[al]WL[978.28];B[ek]BL[808.745];W[lq]WL[972.448];B[lp]BL[789.92];W[kq]WL[971.159]
;B[mq]BL[774.138];W[jo]WL[966.331];B[kn]BL[768.371];W[kk]WL[959.906];B[jk]BL[763.984]
;W[km]WL[956.123];B[jl]BL[760.724];W[jm]WL[955.272];B[im]BL[751.193];W[jn]WL[952.015]
;B[ho]BL[730.69];W[hn]WL[946.271];B[in]BL[724.456];W[io]WL[945.247];B[gn]BL[714.262]
;W[hm]WL[923.864];B[il]BL[711.5];W[go]WL[922.731];B[hp]BL[705.765];W[gm]WL[921.49]
;B[fn]BL[702.99];W[hq]WL[915.2];B[ip]BL[685.151];W[jp]WL[909.285];B[iq]BL[681.106]
;W[fm]WL[898.361];B[em]BL[656.255];W[ir]WL[896.485];B[li]BL[632.187];W[lj]WL[885.063]
;B[ki]BL[623.534];W[en]WL[876.897];B[dn]BL[613.206];W[fo]WL[875.803];B[dj]BL[592.908]
;W[lh]WL[848.427];B[lg]BL[569.792];W[kh]WL[845.832];B[ji]BL[560.988];W[kg]WL[839.643]
;B[lf]BL[554.897];W[jf]WL[832.308];B[pc]BL[537.55];W[mc]WL[785.07];B[ld]BL[528.232]
;W[lc]WL[781.97];B[kd]BL[501.556];W[kc]WL[779.421];B[jc]BL[498.697];W[ke]WL[776.287]
;B[le]BL[472.913];W[id]WL[740.245];B[ic]BL[441.981];W[hc]WL[736.823];B[hb]BL[438.061]
;W[gb]WL[731.389];B[hd]BL[432.041];W[gc]WL[729.528];B[kf]BL[426.942];W[jg]WL[724.914]
;B[je]BL[368.859];W[ie]WL[722.604];B[he]BL[365.466];W[if]WL[719.142];B[gf]BL[324.525]
;W[jb]WL[700.722];B[hh]BL[306.425];W[gg]WL[689.301];B[hg]BL[289.817];W[hf]WL[684.192]
;B[fg]BL[287.054];W[ge]WL[683.02];B[ff]BL[282.083];W[ii]WL[666.896];B[ih]BL[249.732]
;W[fe]WL[638.022];B[ee]BL[245.606];W[ed]WL[636.738];B[fd]BL[236.738];W[gd]WL[634.973]
;B[dd]BL[235.085];W[de]WL[624.843];B[ec]BL[226.848];W[ef]WL[624.054];B[cc]BL[221.54]
;W[ed]WL[621.419];B[dc]BL[206.041];W[fc]WL[618.309];B[bd]BL[203.019];W[ce]WL[615.611]
;B[eb]BL[189.32];W[bb]WL[606.427];B[bc]BL[170.675];W[be]WL[562.706];B[cb]BL[164.394]
;W[da]WL[556.843];B[ea]BL[136.329];W[dh]WL[505.728];B[ei]BL[126.599];W[ne]WL[487.682]
;B[nf]BL[113.478];W[of]WL[486.682];B[oe]BL[104.492];W[ob]WL[417.1];B[pb]BL[95.504]
;W[od]WL[408.152];B[pe]BL[90.221];W[oc]WL[407.33];B[nd]BL[75.994];W[nc]WL[382.796]
;B[md]BL[72.385];W[pa]WL[379.604];B[qa]BL[67.769];W[oa]WL[378.875];B[rb]BL[65.109]
;W[en]WL[355.887];B[mr]BL[34.647];W[lr]WL[352.86];B[gk]BL[5.454];W[jj]WL[349.316]
;OB[5]B[ij]BL[30];W[jh]WL[343.474];OB[5]B[hi]BL[30];W[kj]WL[342.383];OB[5]B[ii]
BL[30];W[mj]WL[340.731];OB[5]B[bg]BL[30];W[bh]WL[332.228];OB[5]B[ch]BL[30];W[bf]
WL[328.148];OB[5]B[dg]BL[30];W[eg]WL[325.08];OB[4]B[gh]BL[30];W[df]WL[323.613];OB[4]
B[kp]BL[30];W[jq]WL[316.629];OB[2]B[ae]BL[30];W[ad]WL[296.999];OB[2]B[ac]BL[30]
;W[hk]WL[276.341];OB[2]B[hl]BL[30];W[gl]WL[275.148];OB[2]B[ik]BL[30];W[fk]WL[274.221]
;OB[2]B[gj]BL[30];W[fj]WL[273.061];OB[2]B[fi]BL[30];W[fa]WL[262.512];OB[2]B[fb]
BL[30];W[ga]WL[255.573];OB[2]B[ca]BL[30];W[sl]WL[238.357];OB[2]B[sk]BL[30];W[sm]
WL[237.318];OB[2]B[ls]BL[30];W[ks]WL[235.246];OB[2]B[ms]BL[30];W[qj]WL[221.173]
;OB[2]B[rj]BL[30];W[qi]WL[218.363];OB[2]B[qh]BL[30];W[ng]WL[209.531];OB[2]B[oh]
BL[30];W[mf]WL[201.685];OB[2]B[mg]BL[30];W[pm]WL[181.026];OB[2]B[ri]BL[30];W[ln]
WL[160.43];OB[2]B[ko]BL[30];W[fn]WL[113.991];OB[2]B[aj]BL[30];W[ap]WL[110.681];OB[2]
B[qs]BL[30];W[fl]WL[106.755];OB[2]B[el]BL[30];W[ej]WL[104.596];OB[2]B[dk]BL[30]
;W[dg]WL[103.741];OB[2]B[di]BL[30];W[ag]WL[76.264];OB[2]B[ai]BL[30];W[ah]WL[73.618]
;OB[2]B[ke]BL[30];W[af]WL[67.806];OB[2]B[ad]BL[30];W[lo]WL[51.658];OB[2]B[mp]BL[30]
;W[jr]WL[50.307];OB[2]B[ak]BL[30];W[ao]WL[47.554];OB[2]B[]BL[30];W[]WL[47.554]TB[si]
[qc][aa][ba][da][ra][sa][ab][bb][db][qb][sb][rc][sc][qd][rd][sd][me][ne][qe][re]
[se][mf][nf][of][pf][qf][rf][sf][gg][ng][og][pg][qg][rg][sg][fh][ph][rh][sh][gi]
[qi][hj][qj][sj][hk][rk][no][nq][oq][nr][or][ns][os][ps]TW[fs][gs][nb][is][js][ss]
[ha][ia][ja][ka][la][ma][na][hb][ib][kb][hs][lb][mb][ic][jc][fd][hd][ee][he][cf]
[bg][nj][mk][ok][nl][ol][gn][sn][bo][ho][so][bp][gp][hp][ip][sp][aq][eq][gq][iq]
[sq][cr][ar][br][dr][er][gr][hr][kr][sr][as][bs][cs][ds][es]C[sadperson [8k]: thx
tictac [8k]: thanks for the game
tictac [8k]: i cannor use thickness it seems
sadperson [8k]: yeah
tictac [8k]:

sadperson [8k]: I made a big mistake in the beginning
sadperson [8k]: so it's tough then
sadperson [8k]: haha
])
Move 45 itself is a mistake, just extend.
To use the thickness you have to have something to do with it, which generally means a weak group of your opponent's to pressure.
With that in mind, black 51 is a pass. 53 is more the right idea, but I think you should follow up with the avalanche or something odd like attaching onto the 3-4 stone-- you want to make something so big on the bottom that white will be forced to make a weak group inside of it. At minimum you want to start something complicated so you can get that thickness involved. With 61, black has fallen far, far behind, with no feasible use for the thickness and no points. There are some tactical errors on both sides in the lower left corner after that (b75 is terrible, b83 misses a chance), but I think they are just a footnote.
Edit: 51 was a really, really, bad time to pass. I think that's at least a 20 point mistake.