A highly skilled team resource received a job offer and is leaving the project soon What should the project manager do to maintain project performance while a new team member is being onboarded?

A software delivery project began having technical impediments. The issue may cause a delay of the deliverables. The technical service team has been working on the issue, but the issue is unresolved even after 1 week of maintenance.
What should the senior project manager do now?

A project manager is assigned to manage a project for a previous client of the company. The project manager was warned that this client will likely try to add extra scope to the project without considering the impact of change on time, cost, quality, and risks.
Which action should the project manager take to help plan and manage the budget and resources?

An agile project manager is evaluating the method that will be used to display the value of the work performed to date. Which method will they select to display to the project stakeholder?

A project manager entered into a contract with a vendor to build a new system. During the acceptance test stage, the project manager noticed that the system quality was not satisfactory.
How should the project manager support their claim to the vendor?