Tenant Refusing to vacate House on expiry of tenure as per Registered Rent Agreement

I am the owner of one flat which I purchased in June 2016 in Delhi. I gave this flat on rent to one Senior Citizen aged 72 years in November 2016 for two years by Rent agreement duly registered at Sub Registrar office. My tenant is staying with his wife, daughter and son. My tenant has reputation of good person in the neighbourhood where as his son is unmarried, dubious character and doesn’t have fixed source of Income. My tenant’s track record of making rental payment was inconsistent in 2018 and generally his son gave reason of his health problem. He made all payments by cash and never asked for receipt. Now, contract is getting expired in October, but my tenant’s son is refusing to move out and insisting to renew the contract for at least for one more year giving health issue of his father as a prime reason and committing to leave premises next year in September. Although we have renewal clause in the Rent Agreement, but it is subject to mutual consent. We have another clause which states that “in the event lessee fails to hand over the vacant physical possession of demised premises to the lessor in accordance with the terms of agreement on its determination the lessee shall be liable to pay the lessor unauthorised used or occupation charges @ Rs5000 per day from date of default till handing over the possession “. We are not interested in renewing contract. My queries are as follows: 1. What shall we do, Renew the contract or go for litigation. 2. If renew, his son is suggesting on making contract in his name instead of renewing existing contract. Whether I renew the existing contract, or shall I go for fresh agreement with his son. 3. If we go for litigation, how much time will court take to conclude. 4. What are the chances that I will get judgement in my favour? 5. What will happen to Rent during interim period of litigation 6. Can I get Rs 5,000/- per day as unauthorised used or occupation charges, as per Rent agreement , for the interim period.