I have tried to translate into Russian the sentence:
I am studying the Russian language on the side.
I.e., I just occasionally spend time on it.
Google Translate says:
Я изучаю русский язык на стороне.
However, I was told by a native speaker of Russian that "на стороне" in this context is not correct, and that "на стороне" is used instead in contexts such as a love affair that a spouse may have "on the side".
However, I have seen examples of "на стороне" such as:
Нет ничего плохого в заработке на стороне.
Он тут подыскивал работёнку на стороне.
... which native speakers said are fine.
What is the essential difference between making money or working on the side, and studying a language on the side?
Were the additional examples I provided okay because there was some negative connotation to the mentioned activity?
What are possible correct ways to translate my original sentence?