As one moves up the levels of learning German (or most other foreign languages, for that matter!), one moves from superficial conversation into deeper subjects and even into controversial topics. For example, in a recent German class we discussed a hotly-debated news item from last year, that Facebook and some firms offered female employees funds to freeze their eggs if they wanted to focus on their career and postpone childbearing.
I understand this controversy and can easily discuss it in English. In German, I must reduce it to basic terms. The terms were so basic that our discussion completely flummoxed (and then horrified) our classmate.
When our teacher asked us what the whole story was about, I said, "Frauen können ihre Eier frieren." That's a direct translation from English and unfortunately I literally said that women can freeze their eggs (i.e., the ones that come from chickens). Our teacher had a huge grin on his face as he said, "du meinst Eizellen." Um, sure, that would make more sense (literally, egg cells), but I hadn't known that word.
We all bumbled through giving more examples. I don't have a strong vocabulary for this topic since it's not really something I talk about in German so I struggled to explain the pros and cons.
Finally, at the end of it, our male classmate raised his hand to admit that he was totally confused. He hadn't recognized the word for "employees" and he wondered why we were talking about eggs and refrigerators. I told him in English that it was "in vitro" and he got it but didn't like the idea at all, saying that one shouldn't be able to just pick up a child out of a refrigerator.
Since I have a very strong imagination, I immediately envisioned a spouse saying, "honey, while you're at the store, will you mind picking up a baby?" and then the person at the grocery store picking up a box with "baby starter kit" marked on it. That was so absurd that I started to smile but then caught myself. After all, our classmate was horrified and I didn't want to make it even worse. Darn that imagination!