Could you please tell me if you can read Taraaweeh prayer in four Raka'h at a time as well as two? Or do you have to read in only two Raka'h at a time?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.

There is no harm Inshaa' Allaah in performing Taraaweeh night prayers by praying 4 Rak'as with two Tashahud and one Salaam. The evidence about this is what 'Aa'ishah had narrated saying: "The Messenger of Allaah never prayed more than 11 Rak'as during Ramadan or otherwise. He would pray 4 Rak'as, and don't ask about how excellent they were or how lengthy they were. Then, he would pray 4 Rak'as, and don't ask about how excellent they were or how lengthy they were, then he would pray 3 Rak'as." [Al-Bukhari and Muslim]

But it is more appropriate to conclude the prayer after every 2 Rak'as for many reasons:

Firstly, this is the number of Rak'as the Prophet predominantly used to perform in night prayers, meaning that he used to conclude the prayer after every 2 Rak'as. The evidence about this is the saying of the Prophet : "The night prayer is performed in twos." [Al-Bukhari and Muslim] The second evidence is what Zayd Ibn Khaalid had said: 'Indeed I am going to watch the prayer of the Prophet tonight…..' At the end of the narration he stated that the Prophet prayed in twos.

Secondly, some Islaamic jurists are of the view that it is not correct to pray 4 Rak'as Taraaweeh prayers with one Tasleem (saying Salaam to conclude the prayer); this is the view of the Shaafi'ee School. Some other jurists are of the view that it is dislikeable to pray 4 Rak'as at once, and this is the view of the Maaliki School. Therefore, there is no doubt that avoiding the difference of opinion is something required and praised.

Allaah knows best.