I pray Namaz 5times a day daily is there any Namaz which we have to sit and pray as I have Seen many people praying that if it's there what is the procedure and how many rakaths

we have two kinds of namaz in one day one of them nessesry that called wajib and one of them not nesesary that called mustahab
we have 5 wajib pray in the one day and also have 5 mustahab pray in one day and one of mustahab pray is a pray that prayed after the isha pray
you can pray it by sitting or standing both of them alloweded but its not wajib