What should one do who missed the second raka'ah of the Maghrib prayer? And should he stand up after the last raka'ah to make it up?

If you miss the first two rak'ahs of Maghrib prayer, then after the Imam's salutation, you perform one rak'ah with Al-Fatiha and a surah, then you recite the tashahhud, then you stand up to perform one rak'ah with Al-Fatiha only, then you give the salutation. This is based on the principle that what the latecomer catches with the Imam is considered the beginning of their prayer.

However, if you miss only the second rak'ah of Maghrib prayer, and you prayed the first and third rak'ahs with the Imam, then after the Imam's salutation, you stand up to perform one rak'ah with Al-Fatiha and a surah, then you give the salutation.