You must prove that you can finance your studies in Germany when applying for your visa in your home country. To do so, you must have a sum of €11,900 at your disposal. This amount is sufficient to finance your studies in Germany for one year. Detailed information on the proof of financial resources can be obtained from the German embassy or consulate in your home country.
Please take this matter seriously and calculate realistically. Students from non-EU countries are only permitted to work 120 days per year. The legal working conditions for international students are strict and failing to comply with them may subject you to expulsion from the country. Please also consider that student jobs are hard to find for foreign students in Germany. Financing your studies in Braunschweig fully or even partially through student jobs is not possible.
Each time you extend your residence permit, you will need to provide this proof of financial resources again. The immigration authorities will decide whether you need to open a blocked account for the amount.