Impossible, because if you move somewhere foreign, you're going to learn the language unconsciously within 6 months. People who have only lived in the US don't know this. It almost takes no effort. The human brain is good at this sort of thing.
On the other hand, I've heard from friends who spent some time in South America that Spanish is an exceptionally easy language to learn, and that they could speak half-way fluently within several months.
To bring in the other extreme, I know people who lived in Japan for years and have only learned fairly rudimentary Japanese.
It is very dependent on the person and the language.
So in other words, you learned German within 6 months.
After 6 months in Vienna I could speak basic German but definitely not work & live without using English most of the time.
There is a big difference between being able to exchange pleasantries & understanding the menu at a restaurant and being able to conduct an intelligent conversation or explain complex ideas in it.
Maybe if you're a construction worker your requirements are different, but you cannot work as a (good) software developer without sharing a high level of understanding of at least one language with your coworkers.