Hi,

For setting the automated action, after activating the developer mode, Settings -> Technical -> Automation -> Automated Action, here create a new record for the this purpose, set the name accordingly. Then in the Model field choose the model Contract(hr.contract) on Trigger Condition choose Based on Timed Condition, select Send Email in Action To Do field and set the Email template, for this you can create a new email template(Settings -> Technical -> Email -> Templates), in the delay after trigger date field set negative value as we need the reminder before the end date.

Thanks