change of major
Your residence permit for studying is bound on a certain purpose. Therefore your residence permit is issued for a concrete major. Take a look on your green paper „Zusatzblatt zur Aufenthaltserlaubnis“ it says exactly for what purpose you are allowed to stay in Germany.
Please note that it is very important to get the permission from the foreign authorty before you change your major. Only with the allowance of the foreign authority you can exmatriculate and enroll for a new major. Please write an e-mail to firstname.lastname@example.org and talk with us about your plans if you think about changing your major.