I really want to know what is proper the cpu temperature for my Mac book
I found two 13" MacBook Pro notebooks which offered a 3.1 GHz i5 CPU with 2 physical cores. Both have a 100°C  TJUNCTION rating for the CPU. (Junction Temperature is the maximum temperature allowed at the processor die.):


MacBook Pro (13-inch, 2016, Four Thunderbolt 3 Ports)


Model Identifier - MacBookPro13,2
Intel® Core™ i5-6287U Processor
TJUNCTION  100°C

MacBook Pro (13-inch, 2017, Four Thunderbolt 3 Ports)


Model Identifier - MacBookPro14,2
Intel® Core™ i5-7287U Processor
TJUNCTION  100°C



So a temperature of 65-75°C is within normal operating range for the CPU.

If neither of these are the MacBook Pro model you have, then please provide the necessary information to properly identify the one you have.