I want to know the time period of a contested divorce on ground of des

My mother and father has been living separately from last 20 years. We are two children of our parents. Both of us are living with my mother from last 22 years. My mother is a government employee, she is going to retire from her service in April, 2020. My father is refusing to sign the Pension papers. My mother wants to get divorce. We want to file a case for contested divorce on ground of desertion and cruelty, as my father will not be ready to get divorce with mutual consent. I want to know how much time it will take to get divorce and can I and my elder sister eligible to get any share of my father's property? Regards