StephaneLamy:
There are too many uncovered variations in this problem. After H8 C9 D9 H9, any move among J5, J6 or J8 should be winning, but is marked incorrect. I would suggest to give up completely on the line H8 C9, who needs so many variations ? In the other lines H8 H9 or H8 J8, many natural ko threats are still missing...

StephaneLamy:
After H8 J8 J6 D1 C2 E9 D9 G9 F9 J5 J4 E9 J5 it says incorrect, but the position is winning for black: either black gets J7, or win the ko at E9. In fact any threat instead of J5 (E3, B6...) should also be correct.