Recourse against commercial hoarding erected on main gate of our residential building

Ours is a residential building on notified commercial street of MPD 2021. Some offices are being operated in our building flats and despite repeated complaints no action is taken by mcd or police against them. Now, one of these offices has erected metal columns and supports on top of the main gate of our building and put its hoarding on it without the permission of other residents. The size of hoarding is more than 6 square meters. I want to know if it is considered a common area or not and if this business can erect such hoarding without our permission? If no, what action can we take against it. These offices are trying to harass other residents to oust them from their properties in order to convert the whole building into commercial. I need legal help in fighting them as the other residents do not seem to be interested in fighting them and are willing to concede to their exploitative offers of buying the other residential houses at cheap rates. Do I have a chance against them?