What is legal aid (Prozesskostenhilfe)?
Court cases and hiring a lawyer cost money. If you cannot bear the costs, you can apply for legal aid which will cover the costs. For legal aid to be granted, chances that you win the lawsuit must be high. In order to receive legal aid, you need to make an application. To do so, you got to fill in the following form: http://www.justiz.de/formulare/zwi_bund/zp1a.pdf
If you have a lawyer or legal aid office help you fill in the form, chances of receiving legal aid are higher since these persons are experienced in completing such applications. The respective court can help you, too.