This dream is rich with symbolism and layered meanings. Let's break it down:

1. Exploring Abandonment: The abandoned building represents parts of your past, possibly childhood memories or experiences that you may have left behind. The various entertainment features like rides and games suggest a longing for joy and innocence from your youth. It could indicate a desire to reconnect with simpler, happier times.
2. The Ripped Dress: The discovery of the little girl’s dress can symbolize lost innocence or unresolved issues from childhood. It may evoke feelings of curiosity about past traumas or experiences that you or someone close to you faced during that time.
3. The Playground and the Noose: This symbolizes a stark contrast between childhood playfulness and darker themes, possibly hinting at underlying fears or anxieties. The noose on the swings may represent feelings of entrapment or a warning about the seriousness of certain situations in your life.
4. Navigating the Abandoned Building: Your struggle to navigate the building, especially with the missing floor, could signify feelings of instability or uncertainty in your life. It might reflect challenges in moving forward or confronting aspects of your past.
5. The Crush and Hookup: The reappearance of an old crush in a setting that feels dilapidated may indicate unresolved feelings or nostalgia. The encounter could symbolize a fleeting moment of connection or desire, which you are aware conflicts with your current situation (having a boyfriend). This aspect of the dream may reflect internal conflict regarding relationships and commitments.
6. Your Niece: The presence of your niece might symbolize your protective instincts or your responsibilities. It indicates that despite exploring these complex emotions, you still have priorities to consider, like family and the well-being of others.
7. The Disappearing Barbecue Tent: The absence of the tent when you leave might signify a loss of comfort or familiarity. It could suggest that after exploring these deeper emotions, you realize certain aspects of your life have changed or are no longer present.

Overall, this dream may indicate a journey through your past, confronting both joyful and painful memories. It suggests a need to reconcile your current life with these experiences, highlighting themes of nostalgia, unresolved feelings, and navigating responsibilities. Reflect on how these themes resonate with your waking life and consider if there are areas where you need to seek closure or understanding.