Clutch and mileage problem

I bought this elite i20 petrol in 2019 December, drove 32000kms till now, as a 1.2ltr engine it does not matches its fuel efficiency, if u drive economically i.e. 70-80 km/h on only highways it gives 16-17 mileage, in city traffic mileage will become 10-12 km/h, on an average it is giving me only 14-15mileage, and recently i have faced clutch hardening and failed problem, my family and me struggled a lot for this problem, in Hyundai service center they told us this problem is being faced in i20 petrol vehicles frequently, so i don't know when the same problem will repeat, the outlook of vehicle is awesome, mileage and clutch hard problems i face in my 3 years of i20 experience . i have been driving cars from 15 years.