Macbook is overheating

Whenever you buy a used computer, you have to find out if there is a warranty that came with them the original owner can transfer by calling AppleCare.

If not, the overheating issue may be one you can only get fixed by paying the repair costs at an Authorized Apple Service Center for out of warranty machines.

You may also find that your machine is under the exchange/repair programs:

Apple Service Programs - Apple Support

And you may also find that the hardware diagnostic is able to isolate a problem:

Use Apple Diagnostics to test your Mac - Apple Support

Now the big question is, what makes you think it is overheating? Is the machine shutting down without warning?

is it just hot to the touch and suddenly freezes a colorwheel cursor?

Are there any optimizers on the machine?

Is it in a well ventilated environment?

If it is sitting on linen, that can prevent proper ventilation. I would also not leave it on your lap either.

If you are using any software that detects the internal heat of the machine, those software are generally inaccurate, and based on specific sensors on specific test bed models. Apple may have changed its sensors since the time those authors wrote the software.

Hi Oliver2733,

Regarding the temperature on your MacBook Pro, check out the information below found in the article here: Keep your Mac notebook within acceptable operating temperatures

"Mac notebooks comply with all temperature limits that are set in national and international safety standards. Make sure to follow the user guide instructions regarding safety and handling. 

Mac notebooks have sensors that detect temperature changes inside your computer. If your Mac notebook has fans, they turn on automatically to cool critical components. 

Tips to manage the operating temperature:

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

It can also benefit you to take a look at your MacBook energy consumption with the help of the article:

View energy consumption in Activity Monitor on Mac

Cheers.