What is the Sunnah regarding the length of Dhuhr prayer and the rest of the five daily prayers, concerning their duration and the surahs (chapters) to be recited by the imam who leads the people? And does the hadith refer to the imam shortening the last two rak'ahs (units of prayer) in bowing and prostration compared to the first two, or merely to reciting only Al-Fatiha?

The Sunnah (definition) for the five daily prayers is to lengthen the recitation in the Fajr (Dawn) prayer, followed by Dhuhr (Noon) in length, to shorten it in Asr (Afternoon) and Maghrib (Sunset) prayers, and to make it of moderate length in the Isha (Night) prayer. The first surah (definition) recited should be longer than the second. As for the last two rak'ahs, only Al-Fatihah is recited in them. The bowing (ruku') and prostration (sujud (definition)) should be proportionate to the length or shortness of the standing (qiyam (definition)). If the standing is long, the rest of the pillars (of prayer) should be lengthened, and if the standing is short, the rest of the pillars should be shortened.