| Game |
| Result | Moves |
Year | Event/Locale | Opening |
| 26. F Sonis vs R G Koellner |
| 1-0 | 93 | 2021 | Mitropa Online Cup | E10 Queen's Pawn Game |
| 27. R G Koellner vs G O Sveinbjornsson |
| 1-0 | 19 | 2021 | European Championship | A45 Queen's Pawn Game |
| 28. L Paichadze vs R G Koellner |
| 1-0 | 61 | 2021 | European Championship | C41 Philidor Defense |
| 29. R G Koellner vs A O Mai |
| 1-0 | 46 | 2021 | European Championship | D05 Queen's Pawn Game |
| 30. R G Koellner vs V Dragnev |
| 0-1 | 76 | 2021 | European Championship | A48 King's Indian |
| 31. K Saraci vs R G Koellner |
| ½-½ | 71 | 2021 | European Championship | C41 Philidor Defense |
| 32. B O Birkisson vs R G Koellner |
| 0-1 | 34 | 2021 | European Championship | A13 English |
| 33. R G Koellner vs T Hillarp Persson |
| ½-½ | 45 | 2021 | European Championship | A45 Queen's Pawn Game |
| 34. A Suleymanli vs R G Koellner |
| ½-½ | 47 | 2021 | European Championship | D50 Queen's Gambit Declined |
| 35. R G Koellner vs J Ferreira |
| ½-½ | 98 | 2021 | European Championship | B52 Sicilian, Canal-Sokolsky (Rossolimo) Attack |
| 36. A Kozak vs R G Koellner |
| 1-0 | 40 | 2021 | European Championship | C53 Giuoco Piano |
| 37. R G Koellner vs M Wecker |
| 1-0 | 21 | 2021 | European Championship | D04 Queen's Pawn Game |
| 38. R G Koellner vs E Romanov |
| 1-0 | 31 | 2021 | DSB Rising Stars GM | D02 Queen's Pawn Game |
| 39. R G Koellner vs L Trent |
| 0-1 | 39 | 2022 | HSK GM | D35 Queen's Gambit Declined |
| 40. R G Koellner vs R Lutz |
| 1-0 | 49 | 2022 | Bundesliga | D02 Queen's Pawn Game |
| 41. J Vykouk vs R G Koellner |
| ½-½ | 50 | 2023 | Mitropa Cup | C50 Giuoco Piano |
| 42. R G Koellner vs S Sahidi |
| 0-1 | 75 | 2023 | Mitropa Cup | A40 Queen's Pawn Game |
| 43. M Sebenik vs R G Koellner |
| ½-½ | 23 | 2023 | Mitropa Cup | D30 Queen's Gambit Declined |
| 44. R G Koellner vs L Dotzer |
| 1-0 | 45 | 2023 | Mitropa Cup | A48 King's Indian |
| 45. L Moroni Jr vs R G Koellner |
| ½-½ | 60 | 2023 | Mitropa Cup | A13 English |
| 46. R G Koellner vs A Kozak |
| 0-1 | 59 | 2023 | Mitropa Cup | A06 Reti Opening |
| 47. M Palac vs R G Koellner |
| 0-1 | 57 | 2023 | Mitropa Cup | D31 Queen's Gambit Declined |
| 48. M Lagarde vs R G Koellner |
| 1-0 | 50 | 2023 | Mitropa Cup | A06 Reti Opening |
| 49. R G Koellner vs F Baenziger |
| ½-½ | 25 | 2023 | Mitropa Cup | A45 Queen's Pawn Game |
| 50. J Schneider vs R G Koellner |
| 0-1 | 39 | 2023 | 50th NRW Cup | C41 Philidor Defense |
Kibitzing
