You need to approach civil court citing danger posed by this illegal structure. Do submit all the documents which u procured through rti. Court will direct authorities like mcd and Delhi police to act as per legal provisions prescribed in law.
Though you have been complaining about illegal construction at various places but you have not got any relief regarding your problem Now you have got details from MCD that it is unauthorized construction .You can write a fresh complaint and with letter of MCD obtained through RTI and photographs of unaurhorised construction ,youcan send to DDA through Whatsapp which is introduced by DDA for noticing complaints about unauthorised constructions .You will get the details for sending your complaint on DDA website and hopefully your complaint will be considered and action will be taken.
Here is a step-by-step guide for you to report an illegal construction that comes to your notice in the city.
Step 1: Download the app DDA 311 on your mobile. The facility is available on Android as well as iOS platforms.
Step 2: Now go to the STF Enforcement Drive Link. Now, you will have to register yourself using your email id or Facebook login. In case you want your identity to remain private, you could generate a unique ID.
Step 3: Now, you click and upload the picture of the property that is constructed illegally on public land. Do note here that your GPS location gets tagged along with the picture when you click and upload it.
Step 4: Select the location where the encroachment has taken place.
Step 5: After providing complaint description, including property details, you could submit the complaint. As soon as your complaint gets registered, you would receive an SMS notifying you about the same.
Step 6: You could track your complaint using your unique ID.
Reference: Government Guidelines