Study means study in Germany. You will have no time for any other activity including learning German. However, I highly recommend you to attend VHS/private language schools during your semester break, you will learn all grammar rules in a systematic way and also receive oral input by a native german speaker. In parallel , you can always read books on Lingq and listen to podcasts/watch Tv shows. In country immersion will work wonders if your listening level is already around B2 otherwise you have no choice but to make efforts to reach it in order to derive benefits from immersion enviornment.
Listening is the most important skill when you are living in your target country. Wherever you go you have to understand locals. You can imagine then comes speaking and reading. Writing, well, now you have ChatGPT and Deepl , you can write something that makes sense if a need arises.
Germany is such a good luck country for foreigners that here every German speaks excellent English. However, German is such a beautiful and flexible language; you will not appreciate it unless you reach an advanced listening level. Learn it just for the sake of enjoying the journey
I can listen to German 24 hours a day even without feeling bored. To give you an analogy, if English is Algebra then German is Calculus 
LOL