Your dream presents some vivid imagery and a narrative that can be analyzed from several angles. Here's an interpretation of the various elements:

1. The Polar Bear: In dreams, animals often symbolize aspects of ourselves or external forces we feel we cannot control. A polar bear can represent a powerful emotion or situation that feels threatening, perhaps something in your waking life that you're avoiding or trying to escape from. The bear chasing you suggests that this issue is persistent and perhaps feels overwhelming.
2. The Chase: The act of running away from the bear and jumping over fences could symbolize your desire to escape from stress or challenges. Fences might represent barriers in your life, and your effort to leap over them indicates your determination to overcome obstacles. However, the bear's continued pursuit implies that you may feel trapped by this situation, unable to fully escape its grasp.
3. The Apartment Building and Balconies: The height and the red umbrellas can signify aspirations or the potential to rise above your challenges. Jumping from balcony to balcony could represent taking risks in order to navigate complex situations in your life. The act of leading the bear to the apartment building suggests a strategy of confronting your fears rather than simply fleeing from them.
4. The Reservoir: This part of your dream introduces a new environment that can symbolize deep emotions or unconscious thoughts. The steepness and height of the reservoir might reflect feelings of vulnerability or the intensity of what you’re dealing with. The presence of another person who mentions "training" suggests that there may be lessons to learn from your experiences, even if they are difficult.
5. Rolling Down the Reservoir: This action may indicate a sense of surrender or acceptance of your current situation. It could imply that you are recognizing the need to let go of control and allow yourself to navigate through your challenges in a more fluid manner.

In summary, your dream seems to be highlighting themes of fear, challenge, and the need to confront rather than avoid difficult situations. It may be beneficial to reflect on what aspects of your life feel overwhelming and consider ways to address them directly, rather than running away. Embracing the lessons that come from facing your fears can lead to personal growth and understanding.