Dzombo , you need to lift the coals from floor of the braai to allow air supply from below .
Take a few bricks , place a grate over it on which to make the fire . The heat will then rise well from the coals through the food above it .
Then , place a screen at the top of your braai opening in front , to help contain the heat . The braai become somewhat like a large open oven , and contains heat inside the body before it goes up the chimney .
The chimney opening also seems quite excessively large , and you need to reduce the size somewhat . This is easily done with a piece of sheetmetal placed on top of the braai , with a hole cut into for smoke to come through .
In the meantime , while experimenting with this , use a large lid over the meat/foodstuffs while braaiing -- it helps to keep the heat on the food
