since Arcmap 10.5 is installed on my computer the icon of all of my old shapefiles appeared with a "?" and cannot be opened anymore. THe error message is " error opening a feature class".
How could I solve this problem?
Have you tried adding the shapefiles to a new empty ArcMap session? Some additional resources can be found at the links below.
What is a shapefile?—Help | ArcGIS for Desktop
How to salvage a corrupt shapefile—Help | ArcGIS for Desktop
Retrieving data ...