Installing grills

Hello sir/ma'am I am residing in one of the apartments in Hyderabad. We are the owners of the flat which is in 4th floor east facing and we have lot of space infront of our flat. Beside to that we have one more flat As my neighbour and we had a huge fight where it gone till hitting each other ,we are planning to install grills infront of our main door which do not disturb any one's way. Alredy in 3rd floor the flat exactly below are alredy installed grills. Can we also do the so and in our apartment we dont have any association And only 5 to 6 owners are residing in the apartment. Can we install grills without blocking any way? Kindly suggest..