Is it possible that you will have to reduce your manpower without sacrificing the quality and its productivity will be the same? Site an example?

Yes, it is possible, and you can achieve this goal by use tools for waste elimination and reduction for the Organization like TPM, WCM, Six sigma and lean, as those tools assist you to reduce the wastage even in manpower available and working time with achieving same quality standards and productivity

example for this Toyota lean system and Ford Vehicle TPM system