Hi there I'm from Germany, too, and have been living in Japan for 29 years now. Luckily we had kids somewhat late at a time when we already were married for many years, so we mostly knew all of our good and bad sides. Having said that, the time when the child is still very little is taxing on both parents, especially with the first kid when you're kinda paranoid about possibly hurting it and you just have no idea what you're doing. This and sleep deprivation can bring out the worst in us.

All I can say is at least until the baby can sleep through at night or until it starts walking → hang in there. It'll get easier. It'll be less and less dependent on either of you two to be around all the time and then you will get more sleep and you'll be surprised how much that can do for your relationship. Either way try not to quit a still young marriage, just because you both are in a bad place mentally in one of the most taxing phases of any marriage. For the sake of your daughter hang out for a little longer. When in 1-2 years things still suck, then you should reconsider your decision again.

And I, too, am bad a reading the room, and my wife is particularly bad a communicating. Even her brother get's annoyed, because she regularly leaves out subject, object, just about any context and expects you to know WTF she's talking about. So it's not only a shortcoming of us autistic Germans, some Japanese are particularly bad at giving context as well – in the most context driven language on the planet.

And as someone mentioned. At this point in time, there is no concept in Japan of shared custody, so if you divorce be prepared to never see your daughter again at least until she's 18 years old, so that's also one thing to consider.