The Text is like Florian wrote.
In English:
Let rest them in your peace and awake to a merry resurrection
Richard Triemer, born 1 Dec 1866, died 18 May 1939
Walter Ehlers, born 5 Jul 1903, died 5 Aug 1970
Margarethe Ehlers, born 23 Jul 1904, died 8 Nov 2000
The day of birth of Margarethe is not sharp. But it must be 23.
About your question:
In Germany a grave should not be touched for about 20 to 30 years (depends from the region). The grave is paid maybe for 25 years. After that you can extend for coming burials of the family. Otherwise the grave will be removed.
When you look to the years of death 1939, 1970, 2000, you can see that there are 31 and 30 years between. So that the grave could be used again.