On the third game, I played as black using my trusty pirc defence meanwhile Mr Sham was using Austrian attack against me. And on move 5 he played a3 , that kind of puzzle me and i have to rethink my counter attack.
Well we played and reach below diagram ,

I saw a mating opportunity
1. ... Rxh3+ 2. Kg1 Rg3 !! ( mating threat )
3. Qxg3 fxg3 4. Bxf8

Now we reach this position .. could you see the mating move/ the winning move.
the move is 4. ..... Qe5+ 5. Ka8 (Mr Sham move and he resign here) Qa5+ 6. Kg1 Qa7#