France has such a law and I am in favor of it.

However that would probably not solve the problem at hand. Food production is a lengthy process (month to years) with high capacity utilization and once production has started it cannot be stopped. Therefore you cannot control for sudden fluctuation in supply and demand. The crop yield for potatoes this year was way better than expected leading to surplus in supply.

I am not aware of anyone starving in Germany and shipping those potatoes to countries where that happens would probably not feasible (in other words with the same money you could probably get better help elsewhere).

I think this is the right thing to do, but this will probably also lead to supermarkets needing to dispose some of their potatoes, because less people buy them and an above average of the free potatoes will probably go bad, because people will get more than they need. So I don‘t think every handed out free potato is a saved potato. Still it is the best option.

There is not a lot you can do if you too much of something at that scale which doesn‘t last. Especially food where the consumption is pretty stable.