Why can time seem to slow down in dangerous situations?
Our perception of time can be distorted in dangerous or highly stressful situations for a few reasons:

Neurologically, our brains process information much more quickly in threatening situations, which can make external time appear to slow down in comparison. The amygdala, our brain's threat detection center, speeds up its processing during danger to help ensure our survival.
This phenomenon may have evolved as an adaptive advantage to help humans respond faster to threats. With time appearing to slow down, we can perceive and react to dangerous events more effectively, increasing the chances of escaping unharmed.
On a psychological level, highly emotional or novel experiences also tend to be more strongly encoded in our memory, which can make them feel subjectively longer in duration. The flashbulb memory effect describes how shocking or significant events can create intensely vivid memories that make the experience of time feel stretched out.

Overall, while time is not actually slowing down, our internal experience of time is altered during dangerous situations due to a combination of neurological, psychological and evolutionary mechanisms that have helped keep us alive in the face of threat. Does this help explain the phenomenon? Let me know if you would like more details or have any other questions!