Problems Getting Maintenance Jobs Done In Flat.

I'm living in a flat that my sister owns in DB Ozone, Dahisar. The maintenance has been slow and, often, they make excuses for why a certain complaint can't be resolved (example: leakage is coming from an upstairs flat and, they don't allow us to enter their flat so, we're putting a plastic bag over your exhaust fan so that while the dripping noise isn't going away, at least the fan won't be short-circuited). There's a build-up of little annoyances in my flat of poor-construction and unattended problems. What kind of lawyer can help me out with this? What would be my level of involvement? And, how much would it cost me? I'm 25, I have never worked with a lawyer before and, I'm worried that a lawyer might drag out the work to try to get more money out of me; any advice about this fear will be appreciated, too.