MacBook Pro 13 2017 temperatures

I recently bought the base version of the MacBook Pro 13 inch 2017.

i noticed that while watching online videos, like movies, the temperatures got really hot, like 70 degree celsius of the cpu , with the fan at 4000 rpm.

I don't know if this is completely normal or if I should contact the assistance . if someone has any advice or answer I'd be very grateful .