(;FF[4]GM[1]SZ[9]ST[2]CA[UTF-8]AP[SGFC:1.15]VW[]

PB[Yusuf]
BR[30k]
PW[Igowin]
KM[0]
RE[W+3]
RU[Japanese]

C[If possible, I would suggest playing online against human opponents, rather than against Igowin.]
;B[cg];W[gc];B[cc];W[gg];B[ec];W[fb];B[ce];W[eg];B[dh]C[Should I have invaded at F5 here instead of playing at D2? Was I too passive?

Yes, I would say so.  If you look at the whole board, you are starting to build a wall slightly to the left of center.  Dividing the board into 2 even territories is a losing strategy for black - you have komi to think about.]
;W[eh];B[ei]C[What was your thinking behind this move?  

How many points of territory would you lose if you let white play, say, D1 first instead?

How many points of territory could you gain if you played elsewhere?]
;W[fi];B[di];W[gh];B[eb]C[Again, was E8 too passive? White's middle right side seems wide open.

Yes - see my comments on move 9.  Simply keeping white out of your side of the board is not sufficient. . .]
;W[ee]C[. . .  and here white has taken the center.  If you were to just complete the boundaries at this point, white has at least half of the territory, and will win.]
;B[df]C[Was D4 the proper defense to white's reduction move at E5 or did I give up more territory going for the peep?

It's not bad, but after white defends the peep, it has a strong wall, and you still have  weaknesses at d3 c2 etc.  Before you peep, look at what the outcome is after the peep is repsonded to.]
;W[ef];B[ed];W[fd];B[fc];W[gd];B[fa]C[You have two choices for putting F8 in atari.  Why did you choose this one?  What would happen if you had chosen the other one?]
;W[gb];B[ea];W[dg];B[ch];W[de];B[cf]C[Should I haven given up the stone at D4 and defended by playing at D6 instead? or was D4 too important? And how exactly do I decide which stones are important anyway?

Do your best to imagine what would happen after the alternatives.  If you lose D4, your group at c3 through e1 starts to look very isolated.]
;W[dd]
(;B[dc]C[Again, should I have blocked at C6 and driven white toward the edge when he invaded at D7?

Since you're considering two basic alternatives, see what would happen for the other one (look at the branch off of the previous move in the SGF).]
;W[cd];B[bd]C[I feel that B6 was a weak defense, was there anything better? White proceeds to tear apart my lines after this.]
;W[af];B[ae];W[bb];B[ac];W[ab];B[bc];W[bf];B[be];W[ga];B[tt]
;W[tt]TW[ha][ia][hb][ib][hc][ic][hd][id][fe][ge][he][ie][ff]
[gf][hf][if][fg][hg][ig][fh][hh][ih][gi][hi][ii])
(;B[cd]C[if you blocked here . . .];W[dc]C[ . . and white, for instance, pushed in again . . . .]
;B[db]C[. . . and you block again,  does your group at the top have enough liberties to survive if white cuts at C8 ?]
))
