What are tenants rights?

I have been staying in a Flat in Bengaluru on Rent for the past three years. I had been paying the rents & maintainence charges regularly till March'2020. During the period of my stay, the owner had agreed to sell the said flat to me. since the documents were not updated in BBMP records, his GPA holder had sought time to rectify the records and get back to me which was taking a long period of time. In the meanwhile, due to Covid-19, I was temporaraily stopped from my employer since i am employed in a Educational Institution and the fate of Educational Institutions is known to every one and could not pay the rent from April'2020. Due to this, I had even offered to pay 50% of the agreed sale consideration and informed the owner to waive-off the monthly rent till the registration of the Sale Deed. But they flaly refused. Now, instead of selling the property to me, they have issued me a legal notice asking me to vacate the flat. My Leave and License Agreement has expired. I have not entered into any sale agreement. I have conversations in what's app about the sale process. I am in a fix. What to do now? Can any assist.