I would ask the supplier about the alloy, if they know then this would be a good start. Assuming by German silver they mean nickel, then nickel sheet works quite well when annealed. In general a non ferrous casting can be worked if the metal was not contaminated or over heated and the casting is not porous or brittle. Sometimes people throw anything into the crucible then the castings can be good or bad depending on how well the metals mix together, or they will put good metal into a crucible which had contaminated metal. For nonferrous bring to black heat then quench in water pickle in a mild acid solution and proceed with the forging/bending process and see how it goes, it will either work or it won't.
