Your local car dealers can help you with the importing of cars, but they have some new cars in their showrooms many times which you can buy from the floor and have it registered in your name and then you have a brand new car without the problems of importing etc. There are quite allot of car dealers in Luanda names like Hyundai, Toyota, Nissan, Peugeot etc. Just ask around of do an google search to locate them in Luanda.
A suggestion might be to look at Nissan since they recently opened a Nissan assembly plant in Viana as far as I know which makes and sells parts locally to Angola also, just confirm this with Nissan before deciding on a Nissan. The majority of parts are scarce in Luanda for most car makes, although it can be imported, which will take time however.
Hope this helps.
