If Germans are allowed to have a permament surplus, than someone MUST always have a deficit.
No country has a trade surplus/deficit of exactly 0, or even near 0. There's always at least half a billion going either way. If you know of any treaties that put limits on these numbers, I'd like to know what they are because I'm very curious about the intentions behind the people who would draft something like that.
Going by https://trade.ec.europa.eu/doclib/docs/2013/december/tradoc_... (link says 2013, but document says Q1 2022), Germany had an intra-EU trade surplus of about 0.2 billion euros. Germany is the closest to a perfect balance within the eurozone in the entire EU except for Bulgaria. Their surplus is almost entirely extra-EU, which isn't a problem for EU members.
The Greeks do hence they are massively in debt. No, they can't export their way out of debt because that would mean Germany has to export less and import more. Germany is supposed to be the workplace country and Greece must remain soulless suburbia with no job opportunities.
Greece can export to any country it wishes, if it has goods or resources that other countries want. If Greece can produce the Germans really want, they'll export to Germany all the way to an internal German trade deficit.
The entire EU would be quite happy if Greece turned into a workers' paradise tomorrow, but no other country is going to pay to fix the mess corrupt Greek governments have left behind unless the Greek situation threatens the stability of their own economies.
Barring an economy from running a surplus seems like a terrible trade deal to me, so I wonder why the Germans would ever agree to such a rule.