OK, now I have fixed my car. It was the water pump . I went to A.T.U for the repair.
A.T.U has like 18 shops in Berlin and even more acoross Germany.
It is really good. You just go there leave your car, the keys etc.- They will then check it out and give you a quote.
The bad thing can be that they are stacked and it might take some time before they get back to you. In my case it took 1 week. And then another week to get the job done!
The total cost was €620. I don't know if it is cheap, but I don't think is over expensive for the work they did on my car (including the new parts).
One thing that pissed me off was that they don't take Visa cards, only EC cards. That pissed me off cause I only had my Visa with me and the ATM would only allow €500 per day on my card. That means that I had to go back home and get the EC card!
All in all I would recommend A.T.U. They seem really professional and they fixed my car (new water pump, new belt,new oil, new oil filter etc).
go to
A.T.U to find the shop closed to you.
PS. The English knowlegde was limited but it worked out just fine.