Landlord has tresspassed into our flat pagdi system

My Mother purcased a Flat in Bandra West on pagdi basis in may,1968. We are staying in the said flat since then , the building changed landlords three times since then , the current landlord is a car dealer who has bought the building in 2011 but has never demanded nor collected rent, infact he has never openly acknowledged the fact he is landlord, sometime in 2015 he hired the services of a Engineerring college to conduct structural audit and it was categorised as C1. My elder brohter was staying in the said Flat . IN 2020 March due to the global lockdown , my bother locked both the eneterances to the Flat and went to stay with his family. Sometime in Nov 2020 the BMC issued notices under sec 354 and the Landlord got the building declared as C1. All tenants and shopkeepers were asked to vacate the buidling. We tenants conducted our own independent Audit by a BMC listed structural firm sometime in Nov 2020. The TAC committee of the BMC had a meeting with our structural engineer and the order was passed in favour of the landlord. We decided to follow the directions of the MCGM and vacated the Flat , some time in March 2021 I received calls that some work is going on in our Flat. The landlord kept calling us to come and collect the area certificate . On March 31 , 2021 when we came to our house and on oepining thed door we found to our dismay a concrete wall built across the house diving the house into 20:80 parts. He had trespassed into our house and put a name plate of an unknown person on the main door. We were shocked and spellbound, when we confronted the Landlord about the wall he feingned ignorance . We filed a coplaint with Khar Police Station on 31 March and that got converted to an FIR on 27 May 2021 In the mean time we were instructed by the police not to file any Civil suit as this FIR was enough. Then in June 2021 we received a call from MCGM officer who told us to come and collect the area certificate. On going to the BMC H west new office we found the area certifcate had the name of one Mr Wasim Ansari below my mothers nae. I refused to accept the same , sometime in Aug 2022 , the FIR was converted into a chargesheet and the Landlord was arrested . The FIR included forgery , trespass and other revelant sections of the IPC. The case stands at the Bombay High Court as the Landlord had filed a Writ petition to squash the FIR smetime in Aug 2020. The question posed here is do we need to file a civil suit , a Declaratiojn of Area Cert making the MCGM a party to this case and also RERA as this would not allow the buidling to be demolished. Please advice as we are anxious and disturbed by the events that have happened. .