My bmi is currently 19.96 yet i have an 32 inch belly.. how much weight should i lose to finally get a flat one? im 161 and 52 kg

Since one can't: Predict how the weight will come off- can't estimate how much weight you need to lose. There's no such thing as natural spot fat loss. You need to lose weight in general ; a certain % will be abdominal fat. Eat healthfully ; be physically active. Calories burned must > calories consumed. To tighten ab's do crunches, reverse crunches, exercise ball crunches, pelvic thrusts, lying leg raises, side.