I wondering to know about the praying time during Rasulullah saw time for Subuh especially because for other time we can clearly see the sun shade and the yellowish sign. During that time they dont have a watch yet and how to define Subuh time especially to end Sahur time. Let say the people live away from the masjid to hear the azan. Can they eat until they see the day light in the morning or how?

At that time they were using different methods.
They were watching the stars movements to know the time, and watching the dawn starts clearly, because there were no lights, and there was no pollution.