[Resolved]  Tata Motors — poor average of tata nexon diesel

I had bought my tata nexon diesel on january 2019 and since then it delivering very poor average.
At first i thought that since the engine is new this problem is there but after 6 months also my average remained low.
Right now the average doesn't go more than 13 kmpl sometimes it also goes less than 10 which is very very less for a diesel. My friends maruti baleno is petrol and gives more than 15 mileage.
Also the acceleration is very poor even in the sports mode, in order to overtake i have to press the full accelerator and only then it accelerates.
Also in the morning when it starts there is heavy white smoke which smells like engine oil and it smokes for almost 10 seconds and there is black smoke visible when i accelerate.
Also the left side passenger glass vibrates a lot when half open.
My neighbours make fun of me saying, "aapne to khatara le li, hamari maruti 800 aapse zyaada achhi hai".
This car has caused a lot of embaressment for me.