Liability of the legal heirs upon the death of the Father

Dear Sirs, We are a family of five persons - father, mother, and three daughters. My father passed away very recently. Now, a person who is a former acquaintance of my father has started to call us (to my father's mobile number) asking us to repay the debts my dad has borrowed. The narration he throws is neither clear nor coherent. Yet, the details he told us over are as follows: 1. My father has borrowed an amount of Rs.7.63 lakhs from a friend of the acquaintance, a bank clerk, the principal and the interest of which is not repaid by my father till date. He didn't mention the interest rate of repayment. Also, the amount borrowed is loaned in the form of cash. The details of the bank clerk, the lender, is neither revealed nor told over to us. 2. Subsequently, my father has borrowed an amount of Rs.5 lakhs from the acquaintance himself, which he says that he transferred through bank. My dad's bank statements does not reflect any amount transferred. When I asked the person to show his bank statements, he didn't send us the same. 3. The person said that the original title deed of my ancestral property is with him, which my father handed over (a copy of the title deed he couriered us). However, there is no promissory note executed by my father. Further, he has sent us an agreement which states that my dad has borrowed money, with no mention of the amount, which is only signed by my dad and the acquaintance (as witness). However, no lender has signed the agreement. And the agreement is not on stamp paper. The agreement was dated in the year 2015. 4. He has shared the whatsapp messages he has communicated over with my dad wherein he has mentioned that on behalf of my father, the person is paying an interest which amounts to Rs.21000 per month. (He told us over that all the interest he paid on behalf of my father to the lender is in cash). 5. Upon our request, he has sent us an excel sheet showing the total amount borrowed as Rs. 16 lakhs (the breakup of which I still don't understand) and an interest of around Rs. 6 lakhs without mentioning the interest rate or the amount repaid by my father, if any. Moreover, in the excel sheet, he has shown the amount of interest paid by him on behalf of my father to the lender is Rs.27000/- for 18 month. Kindly guide us to resolve this maze. So, also let us know how to proceed further.