Can We Recite the Same Surah in Each Rak`ah?
Question

I don’t know many Surahs as I am still learning. I was wondering for the Tarawih prayers, can I repeatedly say the same ones?
Praise be to Allah.There is nothing wrong with repeating the same Surah in Tarawih prayer, or in any other prayer. A person may recite a Surah in the first Rak`ah and repeat the same Surah in the second. The evidence for that is the general meaning of the verse in which Allah says (interpretation of the meaning): 
“Indeed, your Lord knows, [O Muḥammad], that you stand [in prayer] almost two thirds of the night or half of it or a third of it, and [so do] a group of those with you. And Allāh determines [the extent of] the night and the day. He has known that you [Muslims] will not be able to do it and has turned to you in forgiveness, so recite what is easy [for you] of the Quran.” [Al-Muzzammil 73:20] 
Abu Dawud narrated (816) from Mu`adh ibn `Abdullah Al-Juhani (may Allah have mercy on him) that a man from Juhaynah told him that he heard the Prophet (peace and blessings of Allah be upon him) reciting Idha Zulzilat Al-Ard [Az-Zalzalah 99] in both Rak`ahs of Fajr prayer and (he said) I do not know whether the Messenger of Allah (peace and blessings of Allah be upon him) forgot or he recited that deliberately. This report was classified as sound by Al-Albani in Sahih Abu Dawud. 
`Abd Al-`Adhim Abadi (may Allah have mercy on him) said: 
“The Companions were uncertain as to whether the Prophet (peace and blessings of Allah be upon him) repeated the Surah because he forgot, as it was his habit to recite a different Surah in the second Rak`ah to what he had recited in the first, so that was not prescribed for his Ummah, or he did it deliberately to show that it is permissible. So it is uncertain as to whether it is permissible to repeat a Surah or not. If it is not clear whether it is permissible or not, then it is more appropriate to interpret what the Prophet (peace and blessings of Allah be upon him) did as meaning that it is permissible, because the basic principle concerning his actions is that they were done to show what is prescribed, and the idea that he forgot goes against that principle.” (`Awn Al-Ma`bud, 3/23)
Indeed, there is nothing wrong with repeating a Surah or a verse within the same Rak`ah. 
An-Nasa’i (1010) and Ibn Majah (1350) narrated that Abu Dharr (may Allah be pleased with him) said: The Prophet (peace and blessings of Allah be upon him) stood reciting a verse and repeating it until morning came. That verse was (interpretation of the meaning): “If You punish them, they are Your slaves, and if You forgive them, verily, You, only You, are the All-Mighty, the All-Wise” [Al-Ma'idah 5:118]. (Classed as good by Al-Albani in Sahih An-Nasa’i) 
Al-Bukhari (5014) narrated from Abu Sa`id Al-Khudri (may Allah be pleased with him) that a man heard another man reciting “Qul Huwa Allahu Ahad (Say (O Muhammad): He is Allah, (the) One)” [Al-Ikhlas 112] and repeating it. The next day he came to the Messenger of Allah (peace and blessings of Allah be upon him) and told him about that, and it was as if the man did not think much of that. The Messenger of Allah (peace and blessings of Allah be upon him) said: “By the One in Whose hand is my soul, it is equivalent to one-third of the Quran.”  
According to another report: A man stood at the time of the Prophet (peace and blessings of Allah be upon him) reciting “Qul Huwa Allahu Ahad (Say (O Muhammad): He is Allah, (the) One)” [Al-Ikhlas 112] at the end of the night, and he did not do more than that, but the Messenger (peace and blessings of Allah be upon him) approved of his repeating the same Surah. 
Ibn Hajar (may Allah have mercy on him) said: 
“The one who recited it was Qatadah ibn An-Nu`man. Ahmad narrated via Abu Al-Haytham that Abu Sa`id said: Qatadah ibn An-Nu`man stayed up for the whole night, reciting “Qul Huwa Allahu Ahad (Say (O Muhammad): He is Allah, (the) One)” [Al-Ikhlas 112] and he did not recite anything else…. And Ad-Daraqutni narrated another version of this Hadith via Is-haq ibn At-Tabba’ from Malik, in which it says: “I had a neighbour who would spend the night in prayer and would not recite anything other than “Qul Huwa Allahu Ahad (Say (O Muhammad): He is Allah, (the) One)” [Al-Ikhlas 112].” 
We ask Allah to enable you to memorise His Book, and to act upon it. 
For more details, please refer to the following answers: 69915 , 20043 , 171060 , and 7198 .
And Allah knows best.