Food is relatively expensive in Germany. For example, a litre of milk costs 0.5 EUR and bread costs 0.4 EUR.
So for food, at least 150 EUR will be needed per month. (Self-Catering)

Public Transport:  Deggendorf is relatively small, so you may never need public transportation. The city has many taxis and buses. Buses cost 1 EUR for a one-way ride.

Most students walk or use a bicycle.

Accommodation:  Normally costs at least 220 EUR per month

Books & stationery:  You may not be required to buy a book but will need to make photocopies. On average per month, you may need around 30 EUR

Miscellaneous:  70 EUR

In total, you will need around 650 EUR per month

NOTE that during your first month you may need more, because the insurances and other costs have to be included:

Some books that you need for your courses can be borrowed from the library, but still you should budget at least 500 Euro per year for textbooks, off-campus seminar costs, required calculator (Texas Instruments BA II PLUS), and other course materials.

You will need to prove that you have the resources to live and study in Germany for one year. A bank statement showing 7800 Euro on deposit should suffice. Most students can live on a budget of 650 covering all basic living expenses, including accommodation. This will not allow for luxuries, very many social activities, or the costs of maintaining a car.