I've been studying Mandarin Chinese since late 2021. I've made significant progress with that language and intend to continue studying until I reach a degree of fluency comparible to an educated native speaker.
Here are some examples of me speaking Mandarin:
When I initially began to seriously study mandarin, I was very much sold on Stephen Krashen's Input Hypothesis. Nowadays, I still think that languages are acquired when we understand messages, but my own opinion greatly diverges from Krashen's at one very important point, namely, the existance of a critical period, and closing of the language acquisition device. I've heard Krashen say multiple times that he thinks the LAD does not close, implying that adults can acquire language in the same way that children do. Krashen believes that the discrepency in language learning success between adults and children is caused by something he calls the "affective filter," which I interpret as an adult's ego interfering with their ability to acquire the language.
I disagree with the affective filter hypethesis, and I disagree that the LAD stays open. I think that just as people stop growing taller, natural language, as Chomsky puts it, stops growing in our heads. Children acquire their native language effortlessly simply by being situated in an environment where the langauge is used. In contrast, Adults, as far as I can tell, need to put in a lot of intentional effort to make progress. That being said, I don't think that adults lose the ability to acquire language entirely. I believe the solution to second language acquisition lies in analysis of the functions children put to use when processing their language input, determining which of theses functions are lost in adults, and filling in thoes gaps with technology assisted intentional study.
I study with combonation of active immersion, passive listening and spaced repetition. I actively immerse in content such as TV dramas, podcasts, or educational videos about topics I'm interested in. I only watch content that has soft subtitles so that I can look up words and mine sentences using Yomitan and Asbplayer. I use Yomitan to get bilingual definitions for every unknown word. If I encounter a 1T sentence, I create a sentence card out of it. On a good day I'll make 50 sentence cards. I do my Anki reps every morning after waking up. I usually listen to or watch something in Mandarin casually before going to sleep, but I don't look up words at this time.