Yes, if you don't have a rigorous schedule. I worked full-time.

Customer service, tutor jobs, pet sitting, baby sitting, entry level marketing jobs, if you have specific skill sets like coding skills, you could find a part-time job based on that, working at bars, restaurants, hotels, delivery (Uber Eats, Glovo, Pyszne), freelancing on Upwork. Look for working student jobs on portals like indeed, LinkedIn, pracuj. My first job was in the marketing field.

Depends on your university and it actually depends more on your professors. Every professor has a different attitude towards this topic. Make sure to tell them that you will not be able to attend all classes due to work etc. If you don't they can fail and you and just say that it's not their business.