| Oct 25, 2025 | Harff | 1–0 | Poltorak | Round 7: Harff, Marcel - Poltorak, Sebastian | English Opening: King's English Variation, Four Knights Variation, Quiet Line | |
| Oct 24, 2025 | Kawulok | 0–1 | Harff | Round 6: Kawulok, Marek - Harff, Marcel | French Defense: Tarrasch Variation, Open System, Euwe-Keres Line | |
| Oct 22, 2025 | Olcum | 0–1 | Harff | Round 4: Olcum, Ahmet - Harff, Marcel | Indian Defense | |
| Oct 21, 2025 | Harff | 0–1 | Zanan | Round 3: Harff, Marcel - Zanan, Evgeny | English Opening: King's English Variation, Four Knights Variation, Quiet Line | |
| Jun 6, 2025 | Harff | 0–1 | Warmerdam | Round 2: Harff, Marcel - Warmerdam, Max | English Opening: Agincourt Defense | |
| Nov 12, 2023 | Harff | ½–½ | Ehmann | Deutsche Schnellschach-Einzelmeisterschaft 2023 | English Opening: Great Snake Variation | |
| Nov 12, 2023 | Harff | 1–0 | Reichmann | Deutsche Schnellschach-Einzelmeisterschaft 2023 | English Opening: King's English Variation, Reversed Sicilian | |
| Nov 12, 2023 | Pubantz | ½–½ | Harff | Deutsche Schnellschach-Einzelmeisterschaft 2023 | Dutch Defense: Normal Variation | |
| Nov 12, 2023 | Langheinrich | ½–½ | Harff | Deutsche Schnellschach-Einzelmeisterschaft 2023 | French Defense: Horwitz Attack, Papa-Ticulat Gambit | |
| Nov 11, 2023 | Harff | ½–½ | Yelisieiev | Deutsche Schnellschach-Einzelmeisterschaft 2023 | English Opening | |
| Nov 11, 2023 | Harff | ½–½ | Langrock | Deutsche Schnellschach-Einzelmeisterschaft 2023 | English Opening: Agincourt Defense, Catalan Defense Accepted | |
| Nov 11, 2023 | Weber | ½–½ | Harff | Deutsche Schnellschach-Einzelmeisterschaft 2023 | French Defense: King's Indian Attack | |
| Nov 11, 2023 | Kolb | 1–0 | Harff | Deutsche Schnellschach-Einzelmeisterschaft 2023 | Dutch Defense: Leningrad Variation, Warsaw Variation | |
| Oct 5, 2023 | Pezelj | 1–0 | Harff | European Chess Club Cup 2023 | Queen's Indian Defense: Classical Variation, Traditional Variation, Main Line | |
| Jul 8, 2022 | Maze | 1–0 | Harff | Schachbundesliga | Sicilian Defense: Nyezhmetdinov-Rossolimo Attack, Fianchetto Variation | |
| Jul 7, 2022 | Harff | ½–½ | Nikolic | Schachbundesliga | English Opening: Anglo-Indian Defense, Queen's Indian Formation | |
| May 15, 2022 | Harff | ½–½ | Meister | Schachbundesliga | English Opening: Symmetrical Variation | |
| May 14, 2022 | Yankelevich | 1–0 | Harff | Schachbundesliga | Nimzo-Indian Defense: Classical Variation, Noa Variation | |
| Apr 10, 2022 | Bacrot | 1–0 | Harff | Schachbundesliga ab M�rz 22 | French Defense: Advance Variation, Euwe Variation | |
| Apr 9, 2022 | Harff | ½–½ | Dautov | Schachbundesliga ab M�rz 22 | English Opening: Agincourt Defense, Wimpy System | |
| — | Euler | 0–1 | Harff | Deutsche Schnellschach-Einzelmeisterschaft 2023 | French Defense: Advance Variation, Euwe Variation | |
