Builder didn't provide proper quality

I bought flat (2014) in Bangalore and did registration (3rd Oct 2018) but still not take possession. First of all, Builder delayed the project and not giving compensation even mention in agreement. In RERA Builder mention different possession date(Dec 2018) and agreement is a different date(Feb 2017). We did registration and paid a various amount like maintenances, maintenances on GST but builder given me simple receive instead of GST receipt. I have check Quality in my flat and found bedroom few tiles color different, I have asked to change tiles but builder don't have same tiles and they are giving me a different excuse so I asked to change complete flat tiles where the builder is ready to change. I am more worried about Quality because paid lakhs and waited a long time but still not getting good quality. As far as if tiles change, I am Ok to ignore others issue. We are in the final stage so I confused shall I fill case against builder? if I fill case how soon we will get a result? Is there any other way we quickly resolve this matter? Please let me know if you are looking more information.