That might be true for net flows, but it seems that German production does not meet demand at nights very often, as per these statistics: https://www.energy-charts.de/power.htm . I do think that situation will get worse with increased PV installations, as they don't produce during nights. Grid storage is going to be needed.

Of course it's an open market and the German expensive production such as gas turbines will not produce if cheaper power can be imported.

There is another form of import which is much harder to judge. Germany imports a lot of stuff from e.g. China, so in some sense the energy production should offset what energy is used in other countries for the imported stuff.

That is true, but it's true for all countries. And it's a major failure of practically all existing climate and environmental regulations that they don't take this into account.