I play regularly long games (60min each) with Droidfish/Stockfish the depth is always close around 21.
From time to time I overlook taktical flaws in my moves, obviously playing on worse positions against an engine makes no sense, so I take my move back. Technicaly the engine does the same, when it changes the evaluation.
That being said I most of the time end up in endgames that are drawn. With black I have trouble drawing the game but I eventualy will. With white I might have a edge, but the engine just always can hold a draw, somehow blockading the position to force a repetition.
I am a very positional player and i guess that is the reason I get these draws, because I mostly avoid taktical positions. NOTE: I am not going for totaly closed positions, I am playing normal positional chess.
I do not think I can beat the engine with black that would be asking for to much but I will try with white.
I play the Benko Opening wih white (1.g3).
If you are curious here is the last game I played with Droidfish:
[fen ""]
1. g3 d5
2. Nf3 Nf6
3. Bg2 c6
4. O-O Bf5
5. d4 g6
6. a4 Bg7
7. b3 O-O
8. Bb2 e6
9. Nbd2 Nbd7
10. c4 Re8
11. Rc1 Rc8
12. Nh4 Bf8
13. Nxf5 exf5
14. e3 Qa5
15. Nf3 Ne4
16. cxd5 cxd5
17. Ne5 Rxc1
18. Qxc1 Qd8
19. Nd3 Bd6
20. Ba3 Ndf6
21. Bxd6 Qxd6
22. Qc2 Qa3
23. Rc1 h5
24. Qb2 Qd6
25. Ne5 Kg7
26. b4 Re7
27. f3 Ng5
28. Kf2 Ne6
29. h4 Rc7
30. Rxc7 Qxc7
31. Bf1 Nd7
32. Nd3 Nf6
33. a5 Ne8
34. Qc1 Qxc1
35. Nxc1 Nd6
36. Nd3 Nc7
37. Ne5 Ne6
38. Nd7 Nf8
39. Nc5 Ne6
40. Bd3 b6
41. Nd7 bxa5
42. bxa5 Nb7
43. a6 Nbd8
44. Ke2 f6
45. Kd2 Kf7
46. Kc3 Ke7
47. Nc5 Nc7
48. Kb4 Nc6+
49. Ka4 Nd8
50. Bb5 Nde6
51. Bf1 Kd6
52. Kb4 Nf8
53. Bd3 Nfe6
54. Bb5 Ng7
55. Nb7+ Ke7
56. Bd3 Nge6
57. Nc5 Kd6
58. Nb7+ Ke7
It went some moves on but ended in a repetition.
I am not really a fan of 1.e4 or sicilian type positions. I kinda got the opinion that you can not really beat the engine in a long positional game in contrast to human players because the engine makes very few inaccuracies. I guess the most chances are in a complex middle game. (I would still like them to be positional, maybe mixed with taktics)
I couldlnt really find any good (human vs engine) games where the engine was in trouble. I will take a look now at recent engine games stockfish lost maybe that will give me a clue how to beat an engine beast.
Maybe in the mean time you will have some usefull ideas, because that is what we are the best in (for now).