what is the temperature recommended for the Macbook pro ?!

Keep your Mac notebook within acceptable operating temperatures - Apple Support

As internal measured temperatures increase, the fans speeds are also increased in a feedback loop. If the micro controller that runs this feedback loop crashes, the fans will fail-safe revert to Maximum speed within seconds.

If Internal temperature at the Processor approaches 100 degrees C, your Mac will do an emergency power-off to protect itself.

Internal temperature regulation is a job for a micro-controller, not a person. Thinking about this at all is thinking about it way too hard.