Some of the Lubricants agfa used do tend to get stiff. before risking bending something, you might want to have a overhaul done. in most of the shutters of that era, the dial just selects the mount of space available to the timing mechanism. (more space shower action)
the flash sync lever on those proably should be set to "X" which will disengage one timing mechanism inteneded to delay the Opening for a time after the Flash contacts close.
https://www.butkus.org/chinon/agfa/agfa_super_silette/agfa_super_silette.htm is a link to the user manual if you don't already have it.