How does someone who missed part of the prayer make up for the missed rak'ahs after the Imam has said the taslim, and are the two rak'ahs for the person who missed part of the prayer performed with two tashahhuds or with one tashahhud?

If a latecomer missed a part of the prayer with the Imam, then what he caught up with the Imam is considered the beginning of his prayer, and what he missed, he completes. This is based on the Prophet's (peace be upon him) saying: "When you come to the prayer, you should be tranquil. So, whatever you catch up with, pray, and whatever you miss, complete." Therefore, if someone missed the first rak'ah of Maghrib and joined the Imam in the second, this (second) rak'ah is considered his first. When the Imam says the salām, he should perform the remaining rak'ah with Al-Fatihah only, then sit for the tashahhud and say the salām. And whoever joined the third rak'ah of Maghrib, this (third) rak'ah is considered his first. When the Imam says the salām, he should stand up to perform what he missed. He should perform a rak'ah with Al-Fatihah and a surah (which is his second rak'ah), then sit for the first tashahhud. Then he performs the third rak'ah with Al-Fatihah only, then sits for the final tashahhud and says the salām.