Manjaka holds a Master's degree in Accounting, Control, and Auditing from the University of Poitiers, as well as a Master's degree in Management Control and Operational Auditing from INSCAE.

He began his career as an auditor at Geneviève Rabenjamina, where he worked for three years and participated in numerous audit assignments in various sectors such as transit, mass retail, and free trade zones. He joined I&P in 2025.