Illegal construction by upper floor neighbour over common area gap blocking natural light and air e

We have one backside MIG flat in builder apartment whose map was properly approved by GDA with proper planning of cross -ventilation ,lavatory,Air -Conditioner heat outlets and welfare of even backside flats too as per the by laws of GDA. The balconies of flats were constructed in such a way (2-3 feet inside the covered area of our apartment while leaving common area gap between our balconies and adjacent plot,so that if any building is constructed in adjacent plot in future,no effect will be on cross ventilation,light,air,lavatory outlet and a.c outlet.This map was properly approved by GDA planned as per GDA bye laws as per our sale deed. Now one bulding is constructed in our adjacent plot having no effect on us much because of proper planning earlier by the common area gap between our balconies and adjacent plot but our upper floor neighbour namely Mr.partap Singh covered that common area gap illegally without approval by GDA and against the bye laws of GDA ,as soon as adjacent building was constructed and it was in our absence and with this illegal construction our Civic and basic right of natural light ,air,cross ventilation,lavatory and a.c.heat outlet blocked. And the continuous water leakage from that illegal construction deteriorated the railing of our balcony and floor. Now what is the procedure to demolish that ILLEGAL structure and what time will it take for the procedure as for some time my family and me is out of the state ..