Foreign students are only entitled to receive BAföG under very special conditions. This, for example, is the case if the parents have worked in Germany for three years, if one parent is German, if the student is a recognized refugee or married to a German citizen or has a permanent residence permit. The office for financial aid in Paderborn can determine if you are entitled to receive BAföG.
There is an overview on the webpage of the International office which provides you with an average estimate of the monthly expenses. Here you can also find other options on how to finance your studies, for instance scholarships or jobs, at this and other universities. The Deutsche Studentenwerk also offers more information.