You want to take part in a language course in order to learn German? In Berlin many language schools offer German as foreign language, most of these schools are certified; this implies that you may be compensated for your costs. This is the case if the language course is advertised as integration measure. Additionally, if you take part in a European program of ESF, you may be compensated for your costs. However, you should check the conditions for this beforehand, if the costs will be reimbursed only after completion of the course.
Adult education centres offer German foreign language courses as well. These centres are public and often cheaper than private language schools. You could start learning German in your current country already. Many language schools offer online courses.