I'm a native english speaker, and it took me about 4 years to go from no German to functionally fluent. I could hold any conversation no problem, deal with thing like opening a bank account, give a presentation etc... what they don't tell you is that if stop using that language, you'll lose it.
Over a decade later I'm not even sure I could even watch a movie now in German and follow along. Reading is still the easiest thing though.
But anyway, I'm now learning French, very slowly, and I find it much more difficult than German. And since my wife and daughter speak it to each other, there's no danger of me no longer coming in contact with the language.