See this in the case of Greece vs Germany. Germany is trying to boost exports by cutting back on imports. If Greece would retaliate by following the exact strategy there would be less trade between them overall. Meanwhile if both countries tried to boost imports, then both of them would be better off.
How exactly does Germany do it? The government is simply enacting policies to destroy the bargaining power of labor. Yes, Germany is trying to compete with Greece based on labor costs. It's trying to pass off a questionable economic policy that destabilizes the eurozone as strength because of moral attachments to export industries and saving money while blaming the other side for importing its products and borrowing to pay for them. This is why the eurozone is a failure and every country should have its own currency.
The central bank can always just keep printing enough money to keep nominal GDP stable, if they want. No matter how much people want to save.
Sorry, that was a bit sloppy. When we say that eg the Fed prints money, we mean that they buy assets with newly created money.
Typically that asset is government debt. But they have been known to buy other stuff as well. And if they run out of government debt to buy, and nominal GDP still hasn't picked up, they can keep buying up the rest of the world.
Just to keep in mind: real GDP = nominal GDP - inflation.
Printing money like isn't expected to do much for real GDP.
Yes, this I recently learned is called the paradox of thrift. [1]
[1] https://www.investopedia.com/terms/p/paradox-of-thrift.asp