MacBook overheating after less than a month

Just because your laptop feels very warm or even hot, does not mean it is overheating.

Heat is naturally generated by the processors when they are under load, and that load will vary greatly dependent upon what is being asked of the computer at the time.

Your MacBook Air has no fans, therefore it relies on the chassis and external surfaces of the computer for conductive cooling. The computer is engineered to keep itself at proper temps this way.

It has also been designed that the processors will throttle and slow their processing to reduce heat when things become very warm. Eventually, when the Mac has decided that enough is enough, it will shut down. That is the point that indicates an overheated condition.

This is Apple's guidance regarding keeping your Mac cool:

Keep your Mac laptop within acceptable operating temperatures - Apple Support

❝Tips to manage the operating temperature:

• Make sure that you’ve installed all Mac software updates.
• Use your Mac laptop where the ambient temperature is between 50° and 95° F (10° and 35° C). Don’t leave your Mac laptop in your car, because temperatures in parked cars can exceed this range. You should also use your Mac laptop where the relative humidity is between 0% and 95% (noncondensing).
• Use your Mac laptop on a stable work surface that allows for good ventilation. Don’t use your Mac laptop in your bed, on a pillow, or under bedding.
• Don’t put anything over the keyboard. 
• If your Mac laptop has ventilation openings, don't put anything into them. 
• Use only Apple-authorized power adapters. ❞

Anti-virus software, cleaning/optimizer apps, and third party security software are notorious for causing all sorts of problems with macOS including making the system work harder which makes the computer run hotter.

If you have any of these types of apps installed, then uninstall them by following their developer's instructions. These types of apps usually cause more problems than they solve because they interfere with the normal operation of macOS. There is no need to have any of these types of apps on macOS.