German Silver is roughly 50% Copper, 20% Nickel, 30% Zinc.
Bronze is roughly 90% Copper, 10% Tin. It is harder and less ductile than brass so it is easier to break when bending it.
Brass is roughly 75% Copper, 25% Zinc.
Copper, Brass and Bronze are annealed (softened) by heating to a red heat and quenching in water.
I could not find information dealing directly with annealing German Silver, but with its high Copper content, I would expect it to use the same annealing method as Brass or Bronze.
The alloy percentages given above are prefaced with "roughly" because there are hundreds of variations available.
Usually the Brasses and Bronzes which are "white" have higher percentages of the white metal (Tin or Zinc). This often makes them more difficult to bend.
Because of the presence of Nickle in German Silver, it is usually pretty tough stuff to bend, even when annealed.
All castings usually have a rather large crystalline grain structure which is easy to break, so if you need to bend them very much you should anneal them first.
Brass and Bronze sheet metal has a much finer grain structure than castings which allows it to be bent without breaking it. It will "work harden" from bending, so if you need to repeatedly bend it, you should anneal it.
I have found that most of the sand castings we get for muzzleloading furniture are Brass and are quite ductile. Most of the Investment castings available are Bronze and will often break unless annealed before bending.