Owner is not returning our Deposit

Hello Sir, Me and my friends rented a flat in Thane and were living for than 5 years. Our agreement ended on 31st March 2020 and our owner didn't extend it by giving us false promises that he will extend it but due to covid pandemic it got further delayed. Due to covid pandemic, we moved back to our native places but we are still paying our rent i.e. 24K for past 5 months. Now when we have decided to vacate our flat, he is refusing to pay our 1 Lakh deposit. I'm currently in Delhi and ready to go back to Mumbai to complete all the formalities and hand over the keys to him but he is not providing us any date. We tried asking him his mail id to send the Official notice of vacating the flat but he refused to give his mail id. So, In the end we have to send the 1 month advance notice on WhatsApp. And even on WhatsApp he is saying that 'He Don't agree to our terms and condition'. He is continuously asking for the keys and saying that if we don't provide him the keys he will enter the flat in our absence. Sir, please guide us what should we do now.