Elementary stuff. Comments welcome... Thanks again to trucid for his comment
(;AW[fa]AW[fb]AW[fc]AW[gd]AW[ge]AW[he]AW[ie]AW[je]AW[kd]AW[ld]AW[lc]AW[lb]AB[kb]AB[kc]AB[jc]AB[jd]AB[id]AB[hc]AB[hd]AB[gc]AB[gb]AB[ga]AW[hb]AW[ib]AB[ia]C[Black to play and live]AP[goproblems]
(;B[ka]C[];W[me]LB[gf:2]LB[hf:5]LB[if:7]LB[jf:9]LB[kf:11]C[Correct, later K18 is an endgame move. But how big is it ?]LB[ff:-1]
(;B[ff]C[No, Playing K18 prevents or makes a Seki, it is worth some points])
(;B[gf]C[To few, count again])
(;B[hf]C[No, count again])
(;B[if]C[Correct. Preventing or making the Seki is worth 7 Points ( in double gote) Actually it could be worth a bit more depending on the right side, because after white makes the Seki M19 now is a Sente move for white.RIGHT])
(;B[jf]C[Uhm, no! Please count again])
(;B[kf]C[Where should 11(!) points come from ??]))
(;B[jb];W[ka]C[Black dies :(])
(;B[ha];W[ka]C[Black dies :(])
(;B[ja]C[Arghl! Black just died, and white does not need to add a move :(])
(;B[ic]C[];W[ka]C[Black is dead :(]))