There are some valid reasons to use software in English as a German speaker. Main among those is probably translations.

If you can speak English, you might be better of using the software in English, as having to deal with the English language can often be less of hassle, than having to deal with inconsistent, weird, or outright wrong translations.

Even high quality translations might run into issues, where the same thing is translated once as "A" and then as "B" in another context. Or run into issues where there is an English technical term being used, that has no prefect equivalent in German (i.e. a translation does exist, but is not a well-known, clearly defined technical term). More often than not though, translations are anything but high quality. Even in expensive products from big international companies.

This is definitely a problem that can occur, but for the one I was thinking of originally when writing the comment, we had pretty much all the resources available: the company sold internationally, so already had plenty of access to high-quality translators, and the application we were building was in-house, so we could go and ask the teams themselves if the translations made sense. More importantly, the need was also clearly there - many of the users of the application were seasonal workers, often older and less well-educated, in countries where neither English nor German were particularly relevant languages. Giving buttons labels in our users' languages meant they could figure out what they needed to do much more quickly, rather than having to memorise button colours and positions.

You're right that sometimes translation for technical terms is difficult, but the case I experienced far more often was Germans creating their own English words, or guessing at phrases they thought ought to exist because their English was not as good at they believed.

I agree that high quality translations are hard, and particularly difficult to retrofit into an existing application. But unless you have a very specialised audience, they're usually worth it!

UX translations are broken most of the time for most of the software and not just in German. People just pretend it's working and okay, when it's not.

And then developers just do N > 1 ? "things" : "thing" without thinking twice, not use pgettext and all the other things.

Compiler errors or low level error messages in general are a good example. Translating them reduces the ability of someone who doesn't share your language to help you.