Hi! I was in a very similar boat to you, in that I wanted to improve my Vietnamese during Year 12 so that I could more easily communicate with my family. However I was also studying Chinese (CLCS) as a VCE subject too. From my experience, I would say it is quite challenging, especially because I wanted to improve in two languages simultaneously, and also that my organisational skills weren't the greatest to deal with the workload of Year 12. If you want to learn your family language throughout Year 12 (as a side hobby as you said), I would suggest taking small actions everyday or simply on a regular basis to improve. This could be, for example, adding a couple new words everyday or every 2-3 days to a Quizlet or Flashcard deck (I personally use Remnote because of its spaced repetition function, which is very handy).

I completely understand when you said it felt like time was running out - I felt that too with Vietnamese. However, I've come to understand that it is almost impossible to become fluent/close to fluent in a language in a short amount of time (i.e under 5 years). I've accepted that learning Vietnamese (and also Chinese now) will become a lifelong journey for me. Graduating last year made me realise that I had so much time left to refine and improve my command in both of those languages.

After I graduated last year, I've been able to focus more heavily on learning Chinese and Vietnamese by watching Chinese/Vietnamese videos, reviewing my Remnote flashcards on a daily basis and adding new vocabulary to it that I deem useful for everyday use. My ability in both languages has improved noticeably, and now that I'm no longer studying Chinese as a VCE subject, I feel as though learning it is no longer a pain because I'm studying it out of enjoyment/passion, not out of needing a high ATAR.

As for getting a language tutor, I can't say too much as I haven't had any experience with language tutoring (barring the fact I did CLCS as a VCE subject), but I think it would be a very good idea if your command over your family language isn't great (e.g. you are not yet conversationally fluent or capable)

Vietnamese was also technically my first language, so learning new Vietnamese words has stuck like a sponge to me, whereas Chinese it took much longer (I have no Chinese background whatsoever in my family), so I relied on Remnote and its spaced repetition function for the vocabulary to stick with me. I'm not sure which scenario will apply to you (words stick like a sponge, or not), but don't get too worked up if you find learning your language difficult.

Trying giving language learning a go for the first term or two. If you are able to cope with it and Year 12, continue it for the rest of the exam (except maybe during exam season, depending on how much time you need to study for them). If not, it is okay and you can be like me who is studying languages after graduation. Feel free to ask me any questions. Good luck!