You'll come to a spot, you never were before!
Be sure to wear good hiking shoes, a rope and a torch could also be usefull.
Although the given coordinates are not very accurate, the target cannot be overlooked!
When the construction of the dam in Esch-sur-Sûre was finished and the reservoir was filled for the first time in 1959-1960, some of the old roads and bridges connecting the villages around the Sûre were flooded. For this reason, some years before a new road was built between Riesenhof and Esch-sur-Sûre. For the realization of this road the construction of 2 huge bridges were necessary: the first one relying Insenborn to Lultzhausen ("Lëlzer Bréck") and crossing the Ningserbaach, the second one ("2. Bréck") crossing the Dirbech. From the bridges you have scenic views on the upper-Sûre lake... but to find the cache, you'll have to search some meters deeper ;-)
You can find more information in luxembourg language at Wikipedia
Va gur sbhaqngvba, jrfgrea punzore.