In the 1980s, a large-scale landslide occurred during the construction of a bypass around the town Herdecke (NRW), which was stopped by backfilling and secured with prestressed anchors, soil anchoring and a complex drainage concept. A comprehensive measuring system was installed to monitor the slope movements. Since 2021, we have been recording movements using inclinometers, extensometers, anchor force measurements and groundwater measuring points. The lecture presents our experience in measuring and analysing these highly sensitive instruments and discusses challenges in data analysis. Particular attention is paid to the interpretation of long-term measurement series and the recognition of critical movement patterns. The results provide valuable insights for the geotechnical monitoring of slopes and their permanent stabilisation.