Hey Diva! I live in Berlin too and am currently toying with the idea of learning tango and salsa. Just thought to share my two cents on this topic.
There are many private schools giving lessons in tango but they are ridiculously expensive (they all charge in upwards of 10 euro per hour and most have amateurs as instructors). Another option to learn tango is to attend courses offered by many clubs/bars in berlin. They normally have better qualified instructors and have better atmosphere. Checkout
http://www.tangokultur.info/termine_berlin for a list of tango events being held in berlin.
Hochschulsport courses of various universities and fachhochschules are also a very good option. I personally think the quality of hochschule courses is the best, though they lack the mesmerizing atmosphere clubs/bars have. These hochschule courses are also open to non-students, though they have to pay a higher fees, which by the way, is still way less than what one would normally pay for a regular course in a club. You can check out the websites of major hochschulesports in berlin by visiting the sites of their parent schools(HU, TU, FHTW, FHW, FU). But these courses are almost always booked out within days of semester opening. So one has to be prompt in signing up for these courses.
You should also mention your height in this post. I think the biggest consideration while looking for a dance partner should be height. Dancing with a partner of incompatible height poses many practical problems and should be avoided if the sole purpose is to learn to dance.
Good luck!
P