Does your FOOD part include B/f, Lunch, Tea, Dinner? Ask for free laundry also and hopefully the accommodation is fully furnished and equipped? Does the package also include transport? If so, then even USD 2,900 per month is not bad, though you should ask for USD 4,500 since you are being appointed as a Manager.
Remember, ANGOLA is the COSTLIEST COUNTY in the WORLD. All clothes, undergarments, foot-wear, even socks and handkerchiefs should be taken by you from India. The only thing available at reasonable price in Angola is liquor. Rest all things may be priced around 4-10 times costlier than in India.