When we loses first two rakats of salat and we complete it after Imam says salam should we recite any surat after Fateha? and in which faults sajda sahu is compulsory.

1. Refer below.
2. Waajibaat are those items that are necessary to complete the Salaat. If one misses any one of them unknowingly, this mistake can be compensated by performing Sajda-e-Sahw (Sajdah done for mistakes made unknowingly). The method of performing this Sajdah is that after the Tashahhud of the last Rakaat, make one Salaam to the right only and perform two Sajdahs and thereafter read the complete Tashahhud, Durood and Du'aas. Make both Salaams thereafter.
If one does not perform Sajda Sahw or if one misses a Waajib knowingly, it is necessary to perform that Salaat all over again.

and Allah Ta'ala Knows Best

Mufti Ebrahim Desai
FATWA DEPT.

1. Q: When one or two Rakaats are missed of a four Rakaat Fard Salaat (behind an Imaam), how does one complete the missed Rakaat(s) - after Salaam? Do I have to read Surah Fatiha and another Surah or only Surah Fatiha?
A: 1 RAKAAT MISSED; The Muqtadi must recite Surah Faatiha and a Surah. 2 RAKAATS MISSED; The Muqtadi must recite in both Rakaats Surah Faatiha and a Surah.
3 RAKAATS MISSED; In the first Rakaat, the Muqtadi must recite Surah Faatiha and a Surah and then sit for Tashahhud. After Tashahhud, he must stand up for the second missed Rakaat and recite Surah Faatiha and a Surah. In the third missed Rakaat, he must recite Surah Faatiha only.
4 RAKAATS MISSED; In the first two Rakaats recite Surah Faatiha and a Surah. In the second two Rakaats recite only Surah Faatiha. (Shaami vol 2 pg. 346; Lebonon)