It is much better just to embed yourself in the country of the language you want to learn. My Chinese was very bad when I first came to China back in 2002, but I really had no choice because English was not an option in most contexts.

In contrast, I lived in Switzerland for two years and didn't learn a word of French (well, maybe a couple): English was always an option, and I was busy enough working that I had not much time for self study.