Compared to other German study locations, Clausthal-Zellerfeld is relatively cheap. However, you will probably need a little more money than at home. Especially during the first two months, when you have to buy a lot of new things (dishes, books, etc.). Overall, however, you should budget around 900 euros per month for living costs in Clausthal-Zellerfeld (including housing costs of around 230 - 420 euros, health insurance of around 120 euros and the rest for books, food, clothing, etc.).
In general, your expenses will of course depend very much on your individual lifestyle.
If you are still looking for funding, you can find out about funding opportunities in your home country from the German Academic Exchange Service (DAAD).