Why is the first level of your house always cold at 24 Celsius and the second floor is very hot at 32 Celsius even though you have central air conditioning and how can you solve this problem?

One thing to be aware of is that hot air rises. Because of this fact the lower levels will usually start cooler that upper levels. Other contributing factors to your issue could be the insulation in your home, and the location of the temp. guage in you house. Assuming you only have one air conditioning unit you will most likely be unable to solve your issue unless you purchase a complex home cooling system. Many multi-level homes have multiple units so that you can control the home/business temp. more closely. There are sensors that you can buy to put around your house to monitor the temp. which allows you the option to purchase a more ocmplex after market cooling system that will help contol the variance in temp. The way that the units can do that is by monitoring the temp in different rooms and then closing off vents to other locations that do not need the cooling air. As I said earlier, this is rather expensive. That is why many offices, etc. have an issue of one room being way to hot and the others extremely cold. Many larger buildings(similar setup to your home) have sectors. These sectors have guages and when the guage is above the preset then the air turns on for the whole sector. You would want to setup sectors as well to control this issue. Many people do not realize that the sun will heat your home and if your second level is directly absorbing the heat that it will be much warmer. Also be careful if you have windows, they will allow much heat to enter. I would research insulation/window treatments if that were the case.