Don't buy every single textbook
When professors would be honest, they would say: "Reading the textbook is a total waste of time. I'm covering the exam relevant parts in the lecture". But since you are at university, professors obviously won't say that. So if you are not striving to be the "Sheldon" of the class, most of the time, you will be just fine with the lecture slides and your notes. Of course, there will be ones from which exercises are taken from or are relevant in other ways, in which case it's wise to buy them. If you are not sure, check out the book in the library. I promise you will know if you need it or not.
Be brave
I know from experience that for especially a more introverted person, it can be hard to connect with other students right away. BUT you'll have to get over yourself and make some new friends because it's the only way you will survive!!! No, seriously, it is much easier if you can exchange thoughts, results, or whatever with other students. You will not feel so lonely anymore and realize that everyone is going through the same sh*t as you do. So, since studying during Corona has brought some difficulties to meet other students here are some tips for you. Try to engage in class discussions when the professor gives you the chance to chat in breakout rooms and have your camera on so you can at least see each other - it's more personal that way. Or sign up for activities for example check out the offers from Connecting Students, go regularly to the same sports lesson at the ASVZ, or maybe try out one of many Student Associations from the UZH. And last but not least, follow the UZH on social media and engage with people on those platforms - this way you not only stay updated but maybe can connect to other students as well. (And if you are not starting your studies at the UZH, don't worry almost every university has similar offers as well.)
You will be alright
Easy for me to say, right? Let me tell you a short anecdote.
On the way to my final 'banking and finance' exam, my friend asked: "Does everyone has their calculators?" It was just a rhetorical question. Our professor repeatedly told us not to forget our calculators because otherwise, we would not be able to take the exam. As you probably already guessed - I forgot mine - on the kitchen island - AT HOME. So long story short, it was the worst moment in my life, I nearly had a mental breakdown. However, in the end, I passed the exam with a calculator that I bought right before the exam.
What this story tells you is not that you should take your calculator with you wherever you go. No, it should tell you that even if it seems really, really bad, you can make it. Sometimes you might cry but you will make it.