Dear Engineer Sheraz Ahmad,
Please find my reply to your questions as follows:
1 – Activities delayed due to predecessor or successor delay. This is Normal, you need to adjust the relationships or durations in your baseline to fulfill the expected dates.
2 – Activities delayed due to resource leveling. If you are using the P6 automated resource leveling, this could be an issue. I recommend you to make it manually by moving activities and checking how it impacts the schedule accordingly. If you want to learn more about this topic, I recommend the intermediate planning course: https://planningengineer.net/courses/construction-project-planning-intermediate-level-with-p6-excel-powerbi/
3 – Activities that cannot be leveled. Why? maybe you need to consider increasing the duration, working more hours, and splitting the activity into more activities.
4 – permissible limit of total and free float. Activities with excessive total float give a misleading indication when we update the schedule. Therefore, it is not acceptable. You can add more reasonable links to the activities to reduce the total float.
5- if negative lag is not allowed from client what will be the solution? You can change the activity relationship instead of Finish to Start with -ve lag to Start to Start with +ve lag or Finish to Finish with +ve lag.