I have studied about 4 foreign languages (about because of varying levels of effort and involvement). I have found that the only real differentiator in terms of

I have studied about 4 foreign languages (about because of varying levels of effort and involvement). I have found that the only real differentiator in terms of retention and progress (as measured by the likelihood that a native speaker would mistake me as such in person or over text) was the quantity of time that I spent speaking to native speakers. This improved not only my spoken abilities but also my reading abilities, although there is no clear reasoning for why the latter occurred. If at all possible, go to barbers that speak your target language. If you're old enough to drink (or have a good fake) go to bars where your target language is spoken, start listening to news in the target language. Hell, if you're single or have a particularly liberal significant other start dating a guy/girl in your target language. Audio and social exposure can be fantastically productive, as much as reading/writing is good for language acquisition.