Yeah, you are technically correct that it is possible to be an Euro member outside the EU or an EU member outside the Euro.

So it's not impossible for Germany to leave the EU and remain an Euro member.

Just like, technically, it's entirelly possible to fall from a tall bridge and survive, so it's not impossible to jump off a tall bridge and survive.

It's just unlikely in practice and jumping off a tall bridge expecting to survive is either stupidity or insanity.

To see just how ultra-special it would be for a Germany outside the EU to still have full Euro member rights, notice how all non-EU countries which are Euro members have microscopic economies and have very special historic sovereignty arrangements with existing EU members: 2 principalities which are protectorates of France, one territory governed by France half of the year and Spain the other half, and a special enclave in Rome for the Catholic Church.

So my point still stands: Germany leaves the EU, Germany leaves the Euro, though with the tiny possibility that Germany gets all other 26 members - many of which gain massivelly from Germany leaving the Euro and some which have "scores to settle" with Germany on that since back in 2012 - to agree that Germany can stay with full rights (good luck with that, better not do it during an election year in Greece).

Any rational person would evaluate a possibiliy of Germany leaving the EU assuming the most likely consequences in related domains such as Euro membership rather than repeat the same silly fantasism of the Brexiters of assuming "we're special so we can beat the odds" ('cause that worked so well...)

As I've seen in Britain, the highly irrational simpleton Nationalism that presumes some special specialness from having born in a specific geographical area, invariably presumes against all indications that such special country and special people will get all they want from the rest when they leave, and, well ... those who actually get to decide what the EU will concede are the one that stay in the EU and they don't really share the fantasies of the nationalist of the leaving country and are hardly going to act in the leaving nation's best interests.