New to Monday Automations and Can't Update Dependencies

Hi all: we just began using Monday to track implementations in a healthcare technology organization. Currently, I am trying to create a simple automation where when a task is marked as complete, it shows the timeline ending (whether ahead or behind schedule) to the date when the task is marked complete AND any tasks that are dependent automatically are marked as in progress in the status and the start date for the timeline for the next task starts on the same date as the completed dependent on task.

Basic waterfall PMI activities and for some reason none of the automations in Monday can do this. I can generate texts or emails when items are marked as complete and all types of other automations, but I am really struggling with this seemingly simple one. Any expert help? Thanks!