How is the prayer completed if the worshiper joins the Imam after missing some rak'ahs, especially concerning the recitation of Al-Fatihah and other surahs, and how are the missed rak'ahs to be completed?

The majority of scholars hold that whatever the latecomer catches up with the Imam is considered the beginning of his prayer. So, if a worshiper misses the first unit (rak'ah) of the Dhuhr prayer, he should, after the Imam's salutation, perform one unit reciting only Al-Fatiha, and then conclude his prayer with salutations. If he misses three units, he should perform one unit with Al-Fatiha and a short surah, then recite the Tashahhud, and then perform two units reciting only Al-Fatiha for each, and then conclude his prayer with salutations.