Sisters not settling property

We are 3 children of our parents, 2 sisters (married) and 1 brother (me). My mother owned a residential flat. Before her death, she had written and got witnessed a will stating that since my father had bestowed all his belongings to his son (me), my mother's shall be divided equally between her daughters only. This document is in possession of my sisters and I have never seen this myself but some relatives have seen it. Even after my mother's passing, my father stayed in the mentioned flat and took care of my elder sister's children during her office hours, till his passing 2.5 years later from my mother's passing. Now, my elder sister has the possession of the above flat but she doesn't reside there. My father had also bought a residential flat. However, it is bought in his name. My father has not transferred anything legally to me, nor has he bought any property in my name. Of note, though, I have the possession of my father's flat and I currently reside in the same for the last 4-5 years. I had been supporting my father financially also, but no nominee was listed in his bank account either. My father had gotten COVID and I bore all his medical expenses with little help from my elder sister and none from my younger sister. I do not have any knowledge if my father left any will, since he didn't mention anything to me, and I live It has been over 2 years since my father's death but my sisters are not willing to settle the property. They insist on 50:50 ownership of my mother's flat amongst themselves, per her will, and also insist on sharing my father's property and bank balance. As I mentioned, I had been supporting my father financially and he had no income of his own. He was getting family pension from my mother's side but that amount was used during his COVID treatment and account was closed. I have tried talking to sisters through extended family and friends but they are insistent on 50/50 of my mother's property and equal sharing of my father's property. What do I do?