Engine gives unusual noise in 5th,6th gear

My name is Anand from Hridwar uttarakhand, I purchased Tata Nexon XMS patrol model in June 2023 from Meadows tata Haridwar. Now I completed 1900km so far. Initially I was driving up to 4th gear only but later after 2 months post 1st service I started shifting to 5th gear and car gives additional unusual noise in 5, and 6 gear like grinding and knocking missed noise which is over and above normal noise. Also, this car is giving problem with gear shifting it is not smooth at all, hard shifting specially from 1st gear to 2nd gear. Not even comparable gear shifting quality like in Maruti and Hyundai. Though I company to dealer but not getting any response so far. They are saying you drive few more kilometer in 5th gear and see if noise is eliminated or not then they will look at it. I can't understand why that is required if this not running now how it will be better later. Overall car has heavy body and powerful engine but engine gear clutch quality is poor. Earlier I drove Maruti and Hyundai both they were awesome in gear and clutch both and great mileage. Nexon mileage is also poor it is around 14.3 after completing 1900kms.