Salam how to pray tahajud namaz?
praying after Eisha and before fajr at night is one of the best (extra)(nafl/nawafil) prayers(salaah).
as Allah ta3ala commanded his prophet salla-Allahou 3alayhi wa sallam in Quran(the meaning of); " "Establish prayer at the decline of the sun [from its meridian] until the darkness of the night and [also] the Qur’ān of dawn. Indeed, the recitation of dawn is ever witnessed. And from [part of] the night, pray with it as additional [worship] for you; it is expected that your Lord will resurrect you to a praised station. And say, "My Lord, cause me to enter a sound entrance and to exit a sound exit and grant me from Yourself a supporting authority." And say, "Truth has come, and falsehood has departed. Indeed is falsehood, [by nature], ever bound to depart." And We send down of the Qur’ān that which is healing and mercy for the believers, but it does not increase the wrongdoers except in loss."( 17:78-82)
"Is one who is devoutly obedient during periods of the night, prostrating and standing [in prayer], fearing the Hereafter and hoping for the mercy of his Lord, [like one who does not]? Say, "Are those who know equal to those who do not know?" Only they will remember [who are] people of understanding." (39:9)
and as prophet Muhammad (salla Allahou 'alayhi wa sallam said(the meaning of); "O people! spread the salaam/salutation and feed (others with)the food and pray while people are sleeping and you will enter the jannah in salaam/peace"
there is no limited number for the tahajoud prayer, but the most famous are 11 or 13(including the shaf' and watr) that is mean 8 or 10 rak'a and then 2 shaf' and 1 watr.
it can be prayed two rak'a and then another two rak'a, or four four, or all together with one salaam it is possible.. but the most famous is to pray two rak;a and salaam and then another two rak'a...etc. for the shaf3 and witr it can also be combined (three rak'a with one salaam at the end) or 2 alone for shaf' and then seal them with one rak'a watr/witr)
and Allah knows better, assalaamou alaikum.