Welcome, Jakub!
Perhaps a good start would be to familiarize yourself with the Quellensteuer (income tax at source) as discussed here
There are a both a wealth and an income threshold, when you are required to file a tax return. Or you may want to do it voluntary already now, in anticipation of your permit C (permanent residency) status and to avoid any surprises later?
Tax people usually know ETFs with acumulating dividends and tax your additional income accordingly, once you declare your position in such security. Swiss brokers have annual reports that are more aligned with Swiss tax requirements than foreign brokers, but tax people will usually ask nicely if you need to provide something else.