how to set up alerts for cases?

I am new in the company and my boss asked to me to put in place a way to receive an alert or email message for cases asigned to project management resources, may be in a % that can be sent in different % of the time before the due date.

For example

1-I will like give a task to one of my resources within the project management group, the resource should be able to create the case and I will like to receive an email alert for any change in the status or for the completion of the task

2-is there any way to receive an email for example if I have a 50 hours task receive an email once we are in the 50% of the time remaining (25 hours) is not completed.

Receive another email once I am in the 75% of time remaining, then 90% and past due if is not completed by then.

Thanks in advance