Overheating problem while charging I phone 13 pro max

See this support article:--> If your iPhone, iPad, or iPod touch gets too hot or too cold - Apple Support

If you get no help, for your peace of mind, I suggest that you make an appointment (*) and have your device inspected at an Apple Store or AASP (Apple Authorized Service Provider) among this list:--> Apple – Location Selector. After checking it out, they'll give you all the available options.

Regards

Giulio

(*) You can do it:

• Online:--> Genius Bar Reservation and Apple Support Options - Apple;
• Contacting a local Apple Store or AASP among the list provided above;
• Using the "Apple Store" app, available and downloadable from AppStore.

I don’t have the slightest idea why you charge between 40 to 80, as it will shorten the useful life of your battery when compared to the correct way to charge your iPhone. If your phone shuts off and displays a message saying it has to cool off, then it is overheating. If this does not happen it is not overheating.

It is expected to get warm when charging, or just being used. It’s called the Second Law of Thermodynamics. Anything that creates or uses energy does so with some loss. That lost energy is expressed as heat. So when you charge the phone it generates heat in the power source, heat in the charger circuit in the phone, and heat as the energy goes into the battery. The faster the charging, the more heat is generated. Likewise when you discharge the battery; not all of the energy from the battery gets to the circuits that use it. Some of it becomes heat. 

If you use the cellular network for voice or data, converting energy to radio frequency signals is very wasteful; only about 30% of the energy that goes into the network components comes out as radio signals, the other 70% becomes heat. And signal strength matters; a 1 bar signal requires that the phone boost its transmitter power to maintain a connection, and it isn’t linear. 1 bar uses 10 times as much energy as 4 bars. An iPhone 13 with a 5G signal uses about twice as much energy as the same phone with an LTE signal, and 5G towers are still not as densely distributed as LTE, so the signal is likely to be weaker, compounding the problem.