ESN Kraków has a pretty active student community. You can get involved with them by following them on Instagram, or even better, make sure to be added to their private WhatsApp group, so you are kept posted on their activities.
There are also many websites that you can visit to learn about events in Kraków, including Krakow.pl or VisitKrakow.
The Multicultural Center (Centrum Wielokulturowe w Krakowie) offers a variety of events to connect international inhabitants of Kraków with locals.
Here is a list of free museums and the dates you can visit them: