How can I setup an email to training teams who have to approve the training plan

To remind training teamsthat they have X days left before the end of training plan arbitration

This functionality is configurable at the Email Configurations page, being available both for user approvers or user contributors to the task:


 

After defining the configuration, the template email could also be changed to include information about the due date to warn the user, using the tag:

 

Finally, please remember that the emails should be activated within each task in order to work for the respective task plan.