Under powered engine in petrol category

I own a Honda Amaze 2013 Petrol Variant. I feel it's Under powered engine and only 2 people can sit comfortably in the back. Poor suspension. Could have been better in terms of overall performance. Mileage is good if you are maintaining eco driving mode(17-18 km/l) but drops drastically if you hit 110 and above km/h(14-15km/l). Within city, it gives an average of 11-12 km/l. Overall I am not very satisfied with the car.