Fenix 6 pro thermometer sensor

Neither. The sensor is inside the watch and is affected by both your body temperature and the ambient temperature.

Then the temperature make no sense as it's mixed 

Yes the thermometers in wrist devices are useless for most activities. They are generally only accurate for swimming due to being immersed in water, or for cycling if you take it off your wrist and mount it on the handlebars. For other activities if you want accurate temperature you'll have to buy a separate Tempe sensor.

AlFadhel said:

Then the temperature make no sense as it's mixed

You are right, to some extent. Such temperature makes little sense for the user in most cases, however this temperature measurement is essential for proper operation of the barometer.

I still can't understand why the sensor is not able to take body temp in count. There is a watchface which does. Oke, it's not complete accurate, but it shows a better temp which is not ways off.

I'm looking for a way to be able to see the temp sensor value on my mobile app.

I really don't get the point of the temperature setting. Why doesn't it use temperature data from your mobile phone if connected? I don't want to buy an external temperature monitor when I have a mobile in my pocket. The temperature values I am seeing on my runs are roughly: body-temperature - air temperature, but that seems of very little value. 

Do you need to see the temperature while running? How are you using that value?

Here is some info about the use of the temperature sensor:

What's The Point of the Temperature Sensor?

"It’s used to support the barometer. It’s not intended to be used as a reference measure for ambient or body temperature. it is useful when swimming though as you can then understand why you feel cold when swimming in the sea."