Cooler lamp and flashing arrow – WERKSTATT in Berlin and TÜV

Dear Volvo friends, my Volvo 850 LS automatic has had a few problems since the very latest and also has to go to the TÜV in December. I wanted to ask if someone knows a good workshop in Berlin, which is not now Volvo contract workshop for 5,000€. Or a screwdriver, which can look at my cooler. Problem: Cooler lamp lighted again and again over the summer, saw that cooler fluid is lost and refilled. Then the lid of the cooling water bursted, as o I bought a new one. Now the problem is not so strong anymore, but the radiator lamp still glows. In addition, the red arrow has not always flashed since the latest. The temperature indicator remains constant and the car drives smooth. Everything else on the car is great! Can someone help me?