Dreams are highly subjective and can be interpreted in various ways. However, here are some possible symbolic interpretations for the elements in your dream:

1. High rise luxurious apartment building: This may symbolize a desire for success, achievement, or aspirations for a higher social status.

2. Beautiful large stairs and elevators: These could represent opportunities, progression, or the ability to move up in life.

3. Girl you really like: This likely symbolizes romantic or sexual desires, as well as emotional connections and attraction.

4. Great sex: This often signifies intimacy, pleasure, and satisfaction in your waking life. It may also indicate a strong emotional bond with the person involved.

5. Good friend working on a project related to creating efficient energy: This could symbolize your values or interests in making positive changes in the world, contributing to society, or being environmentally conscious.

Overall, this dream may reflect a combination of your desires for success, romantic connection, and personal fulfillment. It suggests that you have a strong emotional connection or desire for intimacy with someone you are attracted to. Additionally, the presence of your friend working on an energy-related project may represent a desire to make a positive impact or pursue intellectual endeavors alongside your personal relationships. Remember, dream interpretation is subjective, so these elements may have unique meanings based on your individual experiences and emotions.