What advice would you give to Hermano Granel in selecting the software development process model? Why? What other recommendations would you make?

The SALTAAROLHA, Lda recently completed a set of plans for the development of a new application for a Ministry, with Dr. Hermano Granel being responsible for the project in the design phase and in the development and construction phase.
Having already been modestly done the requirements design and analysis
phase, his problem was how to process the transition from the design phase to the development phase, selecting the most convenient development process for the case.
The project presented a high complexity unfolded in a set of 10 different modules,very difficult to integrate. The deadline for completing the development of the application was 120 days, which was clearly too short for a single team (whichHermano Granel had) to meet.
The client had great urgency in the application but since it was a state entity,
could not allocate more budget to the project
Money was a problem ...
What advice would you give to Hermano Granel in selecting the software
development process model? Why? What other recommendations would you make?