Anti-crisis analyst: how to catch up the project and not overdo it

A project gets into your hands. Most of the analytical work has been completed, the requirements have been written, and the technical specifications have been agreed, the development is undergoing, there is a list of questions on the requirements. And in a month, you need to conduct acceptance tests. And yes, the one who quit was a very valuable employee, he had three functional specifications in work. By the way, nobody has cancelled your work, and you are preparing to deliver the project at the same time as the three inherited projects.