The solution is a short one, but there are some interesting variations...
(;GM[1]FF[4]CA[UTF-8]AP[CGoban:2]ST[2]
RU[Japanese]SZ[19]KM[0.00]
PW[Weiß]PB[Schwarz]AW[aq][bq][dr][es]AB[bp][cp][dp][ep][fq][fr][cs][fs]PL[W]
(;W[bs]CR[bs]
(;B[br]CR[br]
;W[ar]CR[ar]
;B[as]LB[cr:A]CR[as]C[Black A didn't work, so Black has to accept this ko. RIGHT])
(;B[cr]CR[cr]
;W[cq]CR[cq]
(;B[er]CR[er]
;W[br]CR[br]
;B[ds]CR[ds]
;W[es]CR[es]
;B[ds]CR[ds]
;W[cs]CR[cs]
;B[dq]CR[dq]
;W[es]CR[es]C[This is a better ko than in the solution])
(;B[br]CR[br]
;W[ar]CR[ar]
;B[as]CR[as]
;W[ds]CR[ds]C[White lives, but Black made a mistake])))
(;W[br]CR[br]
(;B[er]CR[er]C[White is dead])
(;B[cr]CR[cr]
;W[cq]CR[cq]
;B[er]CR[er]
;W[bs]CR[bs]C[Black tricked himself here]
;B[ds]CR[ds]
;W[es]CR[es]
;B[ds]CR[ds]
;W[cs]CR[cs]
;B[dq]CR[dq]
;W[es]CR[es]C[This is a better ho than the solution]))
(;W[cr]CR[cr]
;B[br]CR[br]C[White is dead])
(;W[er]CR[er]
;B[cr]CR[cr]
;W[cq]CR[cq]
;B[dq]CR[dq]C[White is dead])
(;W[cq]CR[cq]
;B[er]CR[er]
;W[ds]CR[ds]
;B[dq]CR[dq]
;W[cr]CR[cr]
;B[bs]CR[bs]C[White is dead]))
