Stadium: Court 8 Round: 25 Ground: Clay
| ITF Germany F8 Qual | 2018/07/15 10:30 | Hamish Stewart v Kai Lemstra | 6-3,6-4 |
| ITF Germany F7 | 2018/07/10 11:35 | Klegou, Alexis v Kai Lemstra | 6-7,6-4,6-3 |
| ITF Germany F7 | 2018/07/09 11:00 | Kai Lemstra v Hendrik Jebens | 4-6,6-1,4-6 |
| ITF Germany F7 | 2018/07/09 08:00 | Kai Lemstra v Tim Handel | 4-6,7-5,6-1 |
| ITF Czech Republic F3 Qual | 2018/05/28 08:00 | Kai Lemstra v Recek, Dominik | 2-6,2-6 |
| Czech Republic F2, Singles | 2018/05/22 08:00 | Kai Lemstra v van Den Berg, Bart | 3-6,3-6 |
| ITF Croatia F3 | 2018/03/22 11:30 | Kai Lemstra v Zmak, Deni | 6-4,1-6,4-6 |
| ITF Croatia F3 | 2018/03/21 15:05 | Kai Lemstra v Hu, Xin | 6-2,6-1 |
| ITF Germany F7 | 2018/07/13 11:00 | Vilella Martinez, Mario v Christoph Negritu | 6-2,6-2 |
| ITF Germany F7 | 2018/07/12 10:00 | Baltensperger, Raphael v Christoph Negritu | 6-4,5-7,0-6 |
| ITF Germany F7 | 2018/07/11 10:50 | Christoph Negritu v Adrian Bodmer | 4-6,6-1,6-3 |
| ITF Germany F6 | 2018/07/07 12:00 | Christoph Negritu v Louis Wessels | 3-6,4-6 |
| ITF Germany F6 | 2018/07/06 12:15 | Christoph Negritu v Paul Woerner | 6-4,2-6,6-2 |
| ITF Germany F6 | 2018/07/05 10:00 | Alex Knaff v Christoph Negritu | 2-6,4-6 |
| ITF Germany F6 | 2018/07/04 10:00 | Robert Strombachs v Christoph Negritu | 2-6,1-6 |
| Challenger Heilbronn Qual | 2018/05/13 09:00 | Christoph Negritu v Igor Sijsling | 4-6,0-6 |