Beside the semester contribution you will need about €934 to cover your monthly expenses.
Once in Köthen, you will have to apply for a student residence permit with the local Foreigners’ Office (Ausländerbehörde).
It will be mandatory that you show a proof of financial funds of €934 per month for the whole duration of your visa (normal a year) of your stay with your application for a student residence permit.
For a one-year residence permit this adds up to €11,208. You have to deposit this amount in a blocked account on your name at a German bank. You are only allowed to withdraw a maximum of €934,00 per month from this account. The amount might change over the time.