Your dream about running through your old high school and navigating narrow stairs and hallways suggests a journey into your past, possibly reflecting feelings about your adolescence or unresolved issues from that time. The setting evokes nostalgia but mixed with anxiety, indicating that you may be grappling with memories or experiences that are both familiar and unsettling.

The girl on a scooter could represent a part of your life that feels carefree or playful, contrasting with your feelings of being chased and hiding. This could symbolize a fear of being confronted with something from your past or aspects of yourself that you're not ready to face.

The underground system with pipes and the spooky atmosphere might signify hidden emotions or thoughts that you're trying to avoid. The act of hiding and waiting until the footsteps are gone suggests a desire to escape from pressure or confrontation.

Overall, this dream may be reflecting your current life situation, where you feel the need to navigate through complex emotions or challenges, akin to playing a game of hide and seek. It might be beneficial to explore what aspects of your past or current life feel unresolved or anxiety-inducing, allowing yourself to confront those feelings in a safe space. Consider journaling about these thoughts or discussing them with someone you trust for further clarity.