i used Computer Analysis and i saw a big mistake in his calcualtion, he said that the possition is drawish and actualy it was mate after the last move he calculated and i only analised a few games

1. d4 d5 2. c4 c6 3. Nc3 Nf6 4. Bf4 e6 5. cxd5 cxd5 6. e4? ( 6. e3 Nc6 7. Nf3 Nh5 8. Bg5 Qb6 9. Bb5 Bd7 10. O-O h6 11. Bh4 Bd6 12. Ne5 Nxe5 13. Qxh5 Bxb5 14. Nxb5 Qxb5 15. dxe5 ) ( 6. e4 dxe4 7. Bb5+ Bd7 8. Bxd7+ Qxd7 9. Nge2 Nc6 10. O-O Rc8 11. Bg5 Be7 12. Qa4 O-O 13. Rac1 Rfd8 14. Bxf6 Bxf6 15. Nxe4 Bxd4 16. Nxd4 Qxd4 ) 6... dxe4 7. Bb5+ Bd7 8. Nge2 ( 8. Bxd7+ Nbxd7 9. Nge2 Bb4 10. O-O O-O 11. Qb1 Bxc3 12. bxc3 Qb6 13. f3 Qc6 14. Qb3 Rad8 15. Ng3 exf3 16. Rxf3 Nd5 17. Ne4 ) ( 8. Nge2 Bxb5 9. Nxb5 Bb4+ 10. Nbc3 Nc6 11. O-O O-O 12. Bg5 Bxc3 13. Nxc3 h6 14. Bxf6 Qxf6 15. Nxe4 Qxd4 16. Qxd4 Nxd4 17. Rad1 Rad8 ) 8... Be7 9. Rc1 O-O 10. O-O Nc6? ( 10... Bxb5 11. Nxb5 Nc6 12. Nbc3 Qb6 13. Qa4 Rfd8 14. Be3 Qb4 15. Qc2 Rac8 16. f3 exf3 17. Rxf3 Ng4 18. Rcf1 Nxe3 19. Rxe3 Nxd4 20. Nxd4 Rxd4 ) ( 10... Nc6 11. d5 exd5 12. Nxd5 Nxd5 13. Qxd5 Bf6 14. Rfd1 Qb6 15. a4 Bxb2 16. Qxd7 Rad8 17. Qf5 Bxc1 18. Rxc1 ) 11. Ng3? ( 11. d5 exd5 12. Nxd5 Nxd5 13. Qxd5 Re8 14. Nc3 Bf6 15. Rfe1 Bd4 16. Rcd1 Bxc3 17. bxc3 Bg4 18. Qxd8 Raxd8 19. Rxd8 Rxd8 20. Bxc6 bxc6 21. Rxe4)

How sure are the moves the computer makes? How often this erors occur, did any one else saw this?

Yes, unfornutely he makes often mistakes

yes , my analyzed games too have mistakes which gives off material