To prove your language proficiency in German, the following certificates count as equivalent to DSH 2 (Deutsche Sprachprüfung für den Hochschulzugang):
Regarding language proficiency in English, the following certificates are accepted as proof of European reference level B2:
A certificate of seven years of English language instruction at school
Cambridge Examinations: First Certificate (FCE); Advanced (CAE); Proficiency (CPE)
TOEFL: Paper 500, or Computer 170, or Internet 80
Please note the requirements of the subject you are going to do your doctorate in. In principle, it is the subject your first supervisor at FU Berlin is assigned to.
If you plan to write your dissertation in one of the Romance philologies for example, you need to provide proof of your proficiency in Latin and one additional Romance language. Find further information on Romance language requirements here.