Compared to other European countries, the cost of living in Germany is quite reasonable. The prices for food, accommodation, clothing, cultural events, etc. are basically in line with the EU average. You will need around 500 - 800 Euros a month to cover your living expenses. The largest expense is your monthly rent.
You should expect to pay the following expenses during your stay in Germany:
At Harz University of Applied Sciences you do not have to pay any tuition fees. Ther German Higher Education System is highly subsidised by the government. However, each semester you need to pay a semester contribution. This covers administrative costs and the semester ticket. I It entitles you to use all buses within Wernigerode and Halberstadt for free.
International students may work up to 120 full days or 240 half days (= up to 4 hours per day) per year without any work permit (also applies to EU citizens). You will need an income tax card, which you will receive from the Residence Registration Office.
A work permit is not required when students from foreign universities complete a work placement in Germany, which may last up to 6 months, is factually related to their studies and was approved by the Central Employment Bureau (ZVA) in Frankfurt/Main
If you are working as a student assistant at Harz University of Applied Sciences you won't need a work permit if the annual work hours do not exceed a total of 3 months. If the employment exceeds that, you need to apply for a work permit. In view of the current situation on the German labour market, however, it is relatively difficult to obtain a work permit.