I found the below on findagrave.com while trying to locate family burials.
Is this really true?
If so, how does one find out what happened to family members buried?
Do they remove the bodies or bury new graves above them. Thank you,

Debby Painter, Michigan, USA <gincig@...>

Cemetery notes and/or description: Address:
Große Heimstraße 119, 44137 Innenstadt-West, Dortmund
...Please note that the final resting places in Germany are not eternal,
due to lack of space. This cemetery has a "period of repose" of 20
years. Once the time is up for a renewal of the "lease" the cemetery
administration will place a small sticker on the gravestone to alert the
family to contact the office of the cemetery. Unless the family of the
deceased pays for another period of 30 years, or the grave is of
historical importance (in that case the town will carry the costs), it
will be leveled and re-used. Leftover stones will be collected and
eventually crushed and used as gravel in road construction....