| ITF M15 Troisdorf | 2021/05/12 09:00 | Constantin Schmitz v Tom Kocevar-Desman | 6-4,4-6,3-6 |
| ITF M15 Antalya | 2021/04/14 10:30 | Ivan Sergeyev v Constantin Schmitz | 6-3,5-7,6-3 |
| ITF M15 Antalya | 2021/04/08 06:55 | Flavio Cobolli v Constantin Schmitz | 7-6,7-6 |
| ITF M15 Antalya | 2021/04/06 07:00 | Constantin Schmitz v Bogdan Bobrov | 6-1,6-4 |
| ITF M15 Antalya | 2021/03/30 08:30 | Pol Martin Tiffon v Constantin Schmitz | 6-4,7-6 |
| ITF M15 Antalya | 2021/03/26 07:00 | Georgii Kravchenko v Constantin Schmitz | 6-2,6-3 |
| ITF M15 Antalya | 2021/03/24 07:30 | Constantin Schmitz v Pedro Vives Marcos | 6-3,6-3 |
| ITF M15 Monastir | 2021/03/10 10:30 | Yannick Mertens v Constantin Schmitz | 6-0,6-2 |
| German Premier League | 2020/07/27 17:05 | Paul Valsecchi v Johann Willems | 1-6,7-5,6-2 |
| ITF M15 Monastir | 2020/03/09 13:30 | Johann Willems v Paras Dahiya | 3-6,6-2,6-10 |
| ITF M15 Monastir | 2020/03/09 08:00 | Johann Willems v Lewie Lane | 6-4,6-4 |
| ITF M15 Monastir | 2020/03/08 08:00 | Adil Kalyanpur v Johann Willems | 2-6,2-6 |
| Challenger Koblenz | 2020/02/17 09:00 | Lucas Gerch v Johann Willems | 6-1,6-7,6-1 |
| ITF M25 Nussloch | 2020/01/20 09:00 | Robin Stanek v Johann Willems | 7-5,6-0 |
| ITF M25 Nussloch | 2020/01/19 09:00 | Flemming Peters v Johann Willems | 2-6,0-6 |
| ITF M15 Bad Salzdetfurth | 2019/10/08 11:00 | Jeremy Schifris v Johann Willems | 3-6,6-3,10-3 |