The night prayers are two by two, and Witr is one rakah at the end of the night Sahih Muslim 749 c
Translation
'Abdullah b. 'Umar reported
A man stood up and said. Messenger of Allah, how is the night prayer? The Messenger of Allah (ﷺ) said: The night prayer consists of pair, but if you apprehend the rise of dawn, make it odd number by observing one rak'ah.