Documents To Sell Undisputed Inherited Property

We have a 5 Marla house in Lahore which we want to sell, the house has "Registry" or sale deed in the name of my deceased father who was passed away in 2009, we are 3 siblings (2 sister 1 brother all adults) and a mother.

We have been told, "We cannot sell this house" until we provide some ownership prove aka "Warasti Intiqal".

So my questions are:

  1. What are the document requirements to sell this inherited house?
  2. What is "Warasti Intiqal" and procedure to obtain this?
  3. How much money & time it would take to obtain it?
  4. Do we need to hire someone to obtain this ownership document or we can do it by yourself?

Thanks & regards