> how to pause the progress?
When you cancel a download in progress
(https://www.httrack.com/html/step4.html), HTTrack will let you continue from
where you left off.

> how to resume at the other time?
When you open the project again (https://www.httrack.com/html/step2.html),
choose 'Continue interrupted download' from the action menu.

HTTrack should start again from where it stopped.