Extention of shed for hygienic purposes

I am putting up a PVC shed, an approx 3m front of my bedroom window. I live in the first floor and there is a covered parking below my bedroom which well extends 3m in front of my bedroom and thus a slab of 3m length exists in front of my bedroom. It is a 13 storey building and people in the upper floors above have installed thier AC ducts directly over the slab which drips water over the slab. They also litter sanitary pads, condoms and other garbage which makes the area smelly and mouldy and causes algae and mosquitoes. The association rarely sends a cleaner to clean it (which has to be done daily) and my family members have contracted dengue twice due to the mosquito infestation. During heavy rains water had back-flowed from the water collected in the slab region into my house destroying my wooden furniture (we were in a different city for 2 months during that time and windows were closed but water still overflowed the AC cutout) For this issue i am setting up a PVC shed so that all the water and garbage falling in there slides off to the ground where the garbage man can clean it. But the association head (who happens to live 9 storeys above me) has issues that I'm encroaching a common area (area which is inaccessible without a ladder) for my personal use. This is after I have repeatedly mailed them that the 3m*1.5m slab is and will remain a common area and our attempts are only to keep the area clean on a daily basis so that our family does not contract any diseases. They are threatening a legal action while they too have window grills extending 2ft from thier flat areas for thier own personal purposes.