1. Fill the balloon with hydrogen or nitrogen, which is just a lighter gas than air.
The balloon can fly because the gas in the balloon is lighter than air, but the gas exhaled by our population contains more carbon dioxide, so it is denser than air, so the blowing mouth must be heavy.
3. A balloon inflated by an ordinary air pump can float gently or fall, but it won't fly, because the gas in the balloon is the same as the air.
4. Balloons can fly by introducing a gas with a density lower than that of air, such as hydrogen, and try to use a gas with a density much lower than that of air. This is why hydrogen balloons can fly. But hydrogen is flammable and explosive, so it is not very safe. Pay attention.
Helium is a better gas, which is inert and safe. The inflation step is very simple, and there are instructions after buying the inflation equipment.