A project with a completion time of more than 4 days with several identified activities can be reduced to a completion time of 4 days. This can be done by adjusting the activity timeline of the project and eliminating some of the slack time to meet the earlier completion date. Also, some of the activities can be done in parallel to maximize the time given for the project to be completed. For example, activity A can be done simultaneously with activity B before it proceeds to activity C. You can also use PERT-CPM tool to identify the shortest possible time for project completion.