How can you know the % that should be the follow-up date to determine progress or delays in the schedule?

In order to check the execution of the project in terms of schedule and budget I recommend using the earned value management in the document  here .

Additionally, you can compare the progress of tasks (internal yellow shading of each task) with the current date (vertical dashed line) so that you can graphically check which tasks are delayed.

The same happens for the portfolio of projects.